SEC Info  
    Home      Search      My Interests      Help      Sign In      Please Sign In

American Assets Trust, Inc., et al. – ‘10-Q’ for 3/31/20 – ‘EX-101.DEF’

On:  Friday, 5/1/20, at 4:16pm ET   ·   For:  3/31/20   ·   Accession #:  1500217-20-37   ·   File #s:  1-35030, 333-202342-01

Previous ‘10-Q’:  ‘10-Q’ on 11/1/19 for 9/30/19   ·   Next:  ‘10-Q’ on 7/31/20 for 6/30/20   ·   Latest:  ‘10-Q’ on 10/27/23 for 9/30/23   ·   6 References:   

Find Words in Filings emoji
 
  in    Show  and   Hints

  As Of               Filer                 Filing    For·On·As Docs:Size

 5/01/20  American Assets Trust, Inc.       10-Q        3/31/20   89:10M
          American Assets Trust, L.P.

Quarterly Report   —   Form 10-Q   —   Sect. 13 / 15(d) – SEA’34
Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-Q        Quarterly Report                                    HTML   1.17M 
 2: EX-31.1     Certification -- §302 - SOA'02                      HTML     29K 
 3: EX-31.2     Certification -- §302 - SOA'02                      HTML     29K 
 4: EX-31.3     Certification -- §302 - SOA'02                      HTML     29K 
 5: EX-31.4     Certification -- §302 - SOA'02                      HTML     29K 
 6: EX-32.1     Certification -- §906 - SOA'02                      HTML     27K 
 7: EX-32.2     Certification -- §906 - SOA'02                      HTML     27K 
48: R1          Cover Page                                          HTML     83K 
77: R2          Consolidated Balance Sheets                         HTML    131K 
65: R3          Consolidated Balance Sheets (Parenthetical)         HTML     46K 
23: R4          Consolidated Statements of Comprehensive Income     HTML    137K 
                (Unaudited)                                                      
47: R5          Consolidated Statement of Equity (Unaudited)        HTML    132K 
76: R6          Consolidated Statements of Cash Flows (Unaudited)   HTML    119K 
64: R7          Summary of Significant Accounting Policies          HTML     80K 
21: R8          Acquired In-Place Leases and Above/Below Market     HTML     44K 
                Leases                                                           
49: R9          Fair Value of Financial Instruments                 HTML     83K 
41: R10         Derivative and Hedging Activities                   HTML     45K 
14: R11         Other Assets                                        HTML     46K 
63: R12         Other Liabilities and Deferred Credits              HTML     46K 
73: R13         Debt                                                HTML    121K 
40: R14         Partners Capital of American Assets Trust, L.P.     HTML     31K 
13: R15         Equity of American Assets Trust, Inc.               HTML     82K 
62: R16         Income Taxes                                        HTML     30K 
72: R17         Commitments and Contingencies                       HTML     36K 
39: R18         Leases                                              HTML    127K 
15: R19         Components of Rental Income and Expense             HTML     67K 
57: R20         Other (Expense) Income, Net                         HTML     39K 
89: R21         Related Party Transactions                          HTML     28K 
38: R22         Segment Reporting                                   HTML    124K 
31: R23         Subsequent Event                                    HTML     28K 
56: R24         Summary of Significant Accounting Policies          HTML     68K 
                (Policies)                                                       
88: R25         Summary of Significant Accounting Policies          HTML     51K 
                (Tables)                                                         
37: R26         Acquired In-Place Leases and Above/Below Market     HTML     45K 
                Leases (Tables)                                                  
30: R27         Fair Value of Financial Instruments (Tables)        HTML     78K 
58: R28         Derivative and Hedging Activities (Tables)          HTML     41K 
87: R29         Other Assets (Tables)                               HTML     46K 
69: R30         Other Liabilities and Deferred Credits (Tables)     HTML     45K 
60: R31         Debt (Tables)                                       HTML    104K 
16: R32         Equity of American Assets Trust, Inc. (Tables)      HTML     78K 
42: R33         Leases (Tables)                                     HTML     73K 
70: R34         Components of Rental Income and Expense (Tables)    HTML     68K 
61: R35         Other (Expense) Income, Net (Tables)                HTML     38K 
17: R36         Segment Reporting (Tables)                          HTML    127K 
43: R37         Summary of Significant Accounting Policies          HTML     39K 
                (Details)                                                        
71: R38         Summary of Significant Accounting Policies -        HTML     42K 
                Supplement Disclosures Related to Consolidated                   
                Statements of Cash Flows (Details)                               
59: R39         ACQUIRED IN-PLACE LEASES AND ABOVE/BELOW MARKET     HTML     45K 
                LEASES Acquired Lease Intangibles and Leasing                    
                Costs Included in Other Assets and Other                         
                Liabilities and Deferred Credits (Details)                       
84: R40         Fair Value of Financial Instruments (Details)       HTML     31K 
54: R41         Fair Value of Financial Instruments - Financial     HTML     41K 
                Liabilities Fair Value Measurement on a Recurring                
                Basis (Details)                                                  
24: R42         FAIR VALUE OF FINANCIAL INSTRUMENTS - Carrying      HTML     43K 
                Amount and Fair Value of Financial Instruments                   
                (Details)                                                        
32: R43         Derivative and Hedging Activities (Details)         HTML     70K 
85: R44         Other Assets (Details)                              HTML     62K 
55: R45         Other Liabilities and Deferred Credits (Details)    HTML     48K 
25: R46         DEBT - Summary of Total Secured Notes Payable       HTML     61K 
                Outstanding (Details)                                            
33: R47         DEBT - Summary of Total Unsecured Notes Payable     HTML    126K 
                Outstanding (Details)                                            
86: R48         Debt (Details)                                      HTML    177K 
53: R49         Partners Capital of American Assets Trust, L.P.     HTML     49K 
                (Details)                                                        
67: R50         Equity of American Assets Trust, Inc. (Details)     HTML     49K 
80: R51         Equity of American Assets Trust, Inc. - ATM Equity  HTML     27K 
                Program (Details)                                                
45: R52         EQUITY OF AMERICAN ASSETS TRUST, INC. - Dividends   HTML     30K 
                Declare and Paid on Shares on Common Stock and                   
                Noncontrolling Common Units (Details)                            
19: R53         EQUITY OF AMERICAN ASSETS TRUST, INC. - Summary of  HTML     55K 
                Activity of Restricted Stock Awards (Details)                    
66: R54         EQUITY OF AMERICAN ASSETS TRUST, INC. -             HTML     61K 
                Computation of Basic and Diluted EPS (Details)                   
79: R55         Income Taxes (Details)                              HTML     30K 
44: R56         Commitments and Contingencies (Details)             HTML     89K 
18: R57         LEASES - Narrative (Details)                        HTML     44K 
68: R58         LEASES - Minimum Future Rentals from Noncancelable  HTML     40K 
                Operating Leases (Details)                                       
78: R59         LEASES - Lease Obligations - Minimum Future Rental  HTML     45K 
                Payments from Operating Leases (Details)                         
36: R60         LEASES - Lease Costs & Additional Lease             HTML     42K 
                Information (Details)                                            
27: R61         LEASES - Supplemental Lease Information (Details)   HTML     31K 
52: R62         COMPONENTS OF RENTAL INCOME AND EXPENSE -           HTML     44K 
                Component of Rental Income (Details)                             
83: R63         Components of Rental Income and Expense (Details)   HTML     29K 
35: R64         Components of Rental Income and Expense -           HTML     42K 
                Components of Rental Expenses (Details)                          
26: R65         Other (EXPENSE) INCOME, NET Components of Other     HTML     34K 
                (Expense) Income (Details)                                       
51: R66         Related Party Transactions (Details)                HTML     36K 
81: R67         Segment Reporting (Details)                         HTML     28K 
34: R68         Segment Reporting - Operating Activity Within       HTML     44K 
                Reportable Segments (Details)                                    
28: R69         SEGMENT REPORTING - Reconciliation of Segment       HTML     53K 
                Profit to Net Income Attributable to Stockholders                
                (Details)                                                        
22: R70         SEGMENT REPORTING - Net Real Estate and Secured     HTML     49K 
                Note Payable Balances (Details)                                  
46: R71         SEGMENT REPORTING - Capital Expenditures (Details)  HTML     36K 
75: R72         Subsequent Event (Details)                          HTML     37K 
50: XML         IDEA XML File -- Filing Summary                      XML    161K 
74: XML         XBRL Instance -- aat-20200331_htm                    XML   2.72M 
82: EXCEL       IDEA Workbook of Financial Reports                  XLSX     91K 
 9: EX-101.CAL  XBRL Calculations -- aat-20200331_cal                XML    275K 
10: EX-101.DEF  XBRL Definitions -- aat-20200331_def                 XML    877K 
11: EX-101.LAB  XBRL Labels -- aat-20200331_lab                      XML   1.70M 
12: EX-101.PRE  XBRL Presentations -- aat-20200331_pre               XML   1.10M 
 8: EX-101.SCH  XBRL Schema -- aat-20200331                          XSD    197K 
29: JSON        XBRL Instance as JSON Data -- MetaLinks              356±   543K 
20: ZIP         XBRL Zipped Folder -- 0001500217-20-000037-xbrl      Zip    365K 


‘EX-101.DEF’   —   XBRL Definitions — aat-20200331_def


This Exhibit is an XBRL XML File.


                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<!-- XBRL Document Created with Wdesk from Workiva -->
<!-- Copyright 2020 Workiva -->
<!-- r:92c69077-9e99-4483-8dd1-024c2099730b,g:8816e735-8058-41b1-ad78-fdec622b8e41 -->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
<link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
<link:roleRef roleURI="http://www.americanassets.com/role/CoverPage" xlink:type="simple" xlink:href="aat-20200331.xsd#CoverPage"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/CoverPage" xlink:type="extended" id="if4066e1d9113413990f5c0dcedbadeb7_CoverPage">
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_64c5f9e2-c9a0-44ec-b9c5-37399a9213ee" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_AmendmentFlag"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_AmendmentFlag_64c5f9e2-c9a0-44ec-b9c5-37399a9213ee" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_1a57fba9-f82d-4b8e-90ce-7988b8ffd290" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalYearFocus"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentFiscalYearFocus_1a57fba9-f82d-4b8e-90ce-7988b8ffd290" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_8f0f0fb7-0338-45eb-b8cd-2d548cc5930f" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalPeriodFocus"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentFiscalPeriodFocus_8f0f0fb7-0338-45eb-b8cd-2d548cc5930f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_2a059dca-11ec-4435-9b5f-3c3c0ce17b42" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCentralIndexKey"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityCentralIndexKey_2a059dca-11ec-4435-9b5f-3c3c0ce17b42" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_bbef56d3-2c01-40a4-8533-9f66353522c7" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CurrentFiscalYearEndDate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_CurrentFiscalYearEndDate_bbef56d3-2c01-40a4-8533-9f66353522c7" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_1170a309-c7fb-4d1b-9a9f-b8209cfeac22" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentType"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentType_1170a309-c7fb-4d1b-9a9f-b8209cfeac22" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_8877e144-dde8-47c0-ba3e-6d2e8a848406" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentQuarterlyReport"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentQuarterlyReport_8877e144-dde8-47c0-ba3e-6d2e8a848406" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_5aa13f0a-51f5-457e-a7b8-b2f3b6f52bb6" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentPeriodEndDate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentPeriodEndDate_5aa13f0a-51f5-457e-a7b8-b2f3b6f52bb6" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_763820b6-a478-4c54-abe8-b6bd017a79d8" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentTransitionReport"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentTransitionReport_763820b6-a478-4c54-abe8-b6bd017a79d8" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_bd2872a0-1b6d-474b-a0cb-0f1349e10920" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityRegistrantName"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityRegistrantName_bd2872a0-1b6d-474b-a0cb-0f1349e10920" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_09821954-0c36-490a-a10e-b9decfbbee12" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFileNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityFileNumber_09821954-0c36-490a-a10e-b9decfbbee12" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_921b8568-3990-45f3-8797-504f945f75fb" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityIncorporationStateCountryCode"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityIncorporationStateCountryCode_921b8568-3990-45f3-8797-504f945f75fb" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_86ef0549-2690-4fdc-9503-8f97cfdc1dae" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityTaxIdentificationNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityTaxIdentificationNumber_86ef0549-2690-4fdc-9503-8f97cfdc1dae" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_b6093f5f-eebd-4f13-bb55-a49f9825f8bc" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressAddressLine1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityAddressAddressLine1_b6093f5f-eebd-4f13-bb55-a49f9825f8bc" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_3d0bda79-948f-498f-b1fb-fb671d3bf544" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressCityOrTown"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityAddressCityOrTown_3d0bda79-948f-498f-b1fb-fb671d3bf544" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_ab400fd5-0165-4734-8f8b-3763fd2b172f" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressStateOrProvince"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityAddressStateOrProvince_ab400fd5-0165-4734-8f8b-3763fd2b172f" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_48f94da0-209d-4f2b-a7b8-0c773233be81" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressPostalZipCode"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityAddressPostalZipCode_48f94da0-209d-4f2b-a7b8-0c773233be81" xlink:type="arc" order="16"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_c75d074c-ca07-4431-a8b1-33a4412a9e29" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CityAreaCode"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_CityAreaCode_c75d074c-ca07-4431-a8b1-33a4412a9e29" xlink:type="arc" order="17"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_8d6302ab-ec86-4e9c-822b-88476a320004" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LocalPhoneNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_LocalPhoneNumber_8d6302ab-ec86-4e9c-822b-88476a320004" xlink:type="arc" order="18"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_2cfb08e4-2d4e-4920-a912-aa0535c380b9" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCurrentReportingStatus"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityCurrentReportingStatus_2cfb08e4-2d4e-4920-a912-aa0535c380b9" xlink:type="arc" order="19"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_0b3b5c66-f464-46e6-b55a-e40d94391cc1" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityInteractiveDataCurrent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityInteractiveDataCurrent_0b3b5c66-f464-46e6-b55a-e40d94391cc1" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_74095e5b-f4bb-4cb1-8be9-334c4f8c0fd8" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFilerCategory"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityFilerCategory_74095e5b-f4bb-4cb1-8be9-334c4f8c0fd8" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_a8b98347-3458-4ee2-9a6c-2b48adf4aa2d" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitySmallBusiness"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntitySmallBusiness_a8b98347-3458-4ee2-9a6c-2b48adf4aa2d" xlink:type="arc" order="22"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_191005ca-dd85-49c1-ac7b-e6cf91a7635c" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityEmergingGrowthCompany"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityEmergingGrowthCompany_191005ca-dd85-49c1-ac7b-e6cf91a7635c" xlink:type="arc" order="23"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_dbf048b1-3f17-421e-9924-0d1ae9878f61" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityShellCompany"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityShellCompany_dbf048b1-3f17-421e-9924-0d1ae9878f61" xlink:type="arc" order="24"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_ed1e703d-e4e7-41b6-ba00-7d985276dd02" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_Security12bTitle"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_Security12bTitle_ed1e703d-e4e7-41b6-ba00-7d985276dd02" xlink:type="arc" order="25"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_b1097f15-6c7e-45e3-8b49-814da62d355b" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_TradingSymbol"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_TradingSymbol_b1097f15-6c7e-45e3-8b49-814da62d355b" xlink:type="arc" order="26"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_630d9d10-e8ce-441d-9540-a705099989b1" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_SecurityExchangeName"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_SecurityExchangeName_630d9d10-e8ce-441d-9540-a705099989b1" xlink:type="arc" order="27"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_a79c55a7-77e4-4864-b8f5-a23e13139aca" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCommonStockSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_a79c55a7-77e4-4864-b8f5-a23e13139aca" xlink:type="arc" order="28"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_acad0c3f-391d-4bcc-becc-784f058b7822" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentInformationTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_fa342e1c-0162-4839-bc5c-ba079af7de27" xlink:to="loc_dei_DocumentInformationTable_acad0c3f-391d-4bcc-becc-784f058b7822" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_326b4866-7c92-455b-840c-076f0cc09d19" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_acad0c3f-391d-4bcc-becc-784f058b7822" xlink:to="loc_dei_LegalEntityAxis_326b4866-7c92-455b-840c-076f0cc09d19" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_326b4866-7c92-455b-840c-076f0cc09d19_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_326b4866-7c92-455b-840c-076f0cc09d19" xlink:to="loc_dei_EntityDomain_326b4866-7c92-455b-840c-076f0cc09d19_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_7ad93343-a027-4af6-8299-7bbffc6b32cb" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_326b4866-7c92-455b-840c-076f0cc09d19" xlink:to="loc_dei_EntityDomain_7ad93343-a027-4af6-8299-7bbffc6b32cb" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_5c4b850b-7e06-458e-b905-53ce198cd7cf" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_7ad93343-a027-4af6-8299-7bbffc6b32cb" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_5c4b850b-7e06-458e-b905-53ce198cd7cf" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="aat-20200331.xsd#ConsolidatedBalanceSheets"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ConsolidatedBalanceSheets" xlink:type="extended" id="i435e3e1b1b1d44c6abd3babf8db65476_ConsolidatedBalanceSheets">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_776c1128-b7fa-40d6-b4af-0913bdb1c90d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_776c1128-b7fa-40d6-b4af-0913bdb1c90d" xlink:to="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RentalProperties_92011591-bacd-4835-b465-99a8058207a1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RentalProperties"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_RentalProperties_92011591-bacd-4835-b465-99a8058207a1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressGross_c27b7926-e12c-4439-ae3b-7fe41a35202f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionInProgressGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_ConstructionInProgressGross_c27b7926-e12c-4439-ae3b-7fe41a35202f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAvailableForDevelopment_a858ab50-19fa-4adb-8734-4c2262c32cb2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LandAvailableForDevelopment"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_LandAvailableForDevelopment_a858ab50-19fa-4adb-8734-4c2262c32cb2" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_5fc65d72-7b05-47b5-9f42-936cd1d35aff" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_5fc65d72-7b05-47b5-9f42-936cd1d35aff" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_e263514d-64b2-41d0-a0bc-35b7ee5a617c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_e263514d-64b2-41d0-a0bc-35b7ee5a617c" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_ae2a7a54-3cdb-485f-b542-606039bf6126" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_ae2a7a54-3cdb-485f-b542-606039bf6126" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d02e9345-adda-47ed-9f57-745e402b88d9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_d02e9345-adda-47ed-9f57-745e402b88d9" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_cefb0cd7-1f81-42b7-ba71-4b95b149c201" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_cefb0cd7-1f81-42b7-ba71-4b95b149c201" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_379ad738-d855-4b82-a2c8-446e23c588f7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_AccountsReceivableNet_379ad738-d855-4b82-a2c8-446e23c588f7" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentReceivablesNet_3998da79-3107-423a-b545-90118ca1e242" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredRentReceivablesNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_DeferredRentReceivablesNet_3998da79-3107-423a-b545-90118ca1e242" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_dae4960c-b31c-4924-a1ca-67869859295d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherAssets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_OtherAssets_dae4960c-b31c-4924-a1ca-67869859295d" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_56c29328-7011-4866-a50b-6cc366dc1125" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Assets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0e4c9708-28be-490d-9c74-25828a46009f" xlink:to="loc_us-gaap_Assets_56c29328-7011-4866-a50b-6cc366dc1125" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_776c1128-b7fa-40d6-b4af-0913bdb1c90d" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_192b1840-8ea1-4e73-b9de-3e1ef729f421" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuredDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_SecuredDebt_192b1840-8ea1-4e73-b9de-3e1ef729f421" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebt_b31732ce-d6b8-4b59-b625-6f9ca562fa16" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnsecuredDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_UnsecuredDebt_b31732ce-d6b8-4b59-b625-6f9ca562fa16" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_04b30b51-17cd-42de-bdda-f2a50568bc25" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_LineOfCredit_04b30b51-17cd-42de-bdda-f2a50568bc25" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_83f72e17-97d3-46fb-8c93-a772fc9d35c9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_83f72e17-97d3-46fb-8c93-a772fc9d35c9" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecurityDepositLiability_27d647d8-34c4-423a-bf21-3f0f62cd65c0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecurityDepositLiability"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_SecurityDepositLiability_27d647d8-34c4-423a-bf21-3f0f62cd65c0" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCreditsAndOtherLiabilities_73f40f30-a146-464a-9c69-af2cee0543ff" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredCreditsAndOtherLiabilities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_DeferredCreditsAndOtherLiabilities_73f40f30-a146-464a-9c69-af2cee0543ff" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_2a7a7f2c-fb8d-4f79-8b99-9a89cd9711ce" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Liabilities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_Liabilities_2a7a7f2c-fb8d-4f79-8b99-9a89cd9711ce" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_c5a99f2f-06f8-4785-9176-46210b526344" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_CommitmentsAndContingencies_c5a99f2f-06f8-4785-9176-46210b526344" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_9ed9fb37-3a95-4f44-bfff-bb374ab326b6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_9ed9fb37-3a95-4f44-bfff-bb374ab326b6" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_9ed9fb37-3a95-4f44-bfff-bb374ab326b6" xlink:to="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_c81d0fa4-6c7e-4095-af54-845d5427600a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:to="loc_us-gaap_CommonStockValue_c81d0fa4-6c7e-4095-af54-845d5427600a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_04bd49fd-90a5-4540-9284-310c1e195324" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_04bd49fd-90a5-4540-9284-310c1e195324" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8ae6c873-178f-4f61-a6f2-6edb1e3dca45" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_8ae6c873-178f-4f61-a6f2-6edb1e3dca45" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8448bcbe-4c86-438b-ab87-73f2fb8e45dd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8448bcbe-4c86-438b-ab87-73f2fb8e45dd" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_082f8a40-b863-4cb8-9710-99bde11056cd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_aea55f6f-b111-47cc-bed0-3d0f3c766cdd" xlink:to="loc_us-gaap_StockholdersEquity_082f8a40-b863-4cb8-9710-99bde11056cd" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_4099a0e8-73c4-46a3-8e98-a75c43f4e3e5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_9ed9fb37-3a95-4f44-bfff-bb374ab326b6" xlink:to="loc_us-gaap_MinorityInterest_4099a0e8-73c4-46a3-8e98-a75c43f4e3e5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_23ae64d7-170c-44f7-b1f6-0cc1314f3b60" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_9ed9fb37-3a95-4f44-bfff-bb374ab326b6" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_23ae64d7-170c-44f7-b1f6-0cc1314f3b60" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAbstract_85aa336e-be24-49e7-a58f-33434ac391dc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_PartnersCapitalAbstract_85aa336e-be24-49e7-a58f-33434ac391dc" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccount_520ad964-7c65-4120-84e3-ea55455f328c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnersCapitalAccount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnersCapitalAbstract_85aa336e-be24-49e7-a58f-33434ac391dc" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccount_520ad964-7c65-4120-84e3-ea55455f328c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccount_27d51e63-4dd3-42b2-a6ea-ef72380a823b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralPartnersCapitalAccount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnersCapitalAbstract_85aa336e-be24-49e7-a58f-33434ac391dc" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccount_27d51e63-4dd3-42b2-a6ea-ef72380a823b" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_dee4f6a2-cb48-4d8e-a7ec-aa3cea318987" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapital"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnersCapitalAbstract_85aa336e-be24-49e7-a58f-33434ac391dc" xlink:to="loc_us-gaap_PartnersCapital_dee4f6a2-cb48-4d8e-a7ec-aa3cea318987" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_a1ae84dd-e8b9-4f15-bcc9-4027b30f3558" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_7c3ef3bb-1d6f-4c8f-8e78-cda9d8e1a706" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_a1ae84dd-e8b9-4f15-bcc9-4027b30f3558" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_471346f0-4e1a-46a8-82eb-78d92f79a448" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_776c1128-b7fa-40d6-b4af-0913bdb1c90d" xlink:to="loc_us-gaap_StatementTable_471346f0-4e1a-46a8-82eb-78d92f79a448" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_2b2eee02-092e-4673-a3e2-0403cd692518" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_471346f0-4e1a-46a8-82eb-78d92f79a448" xlink:to="loc_dei_LegalEntityAxis_2b2eee02-092e-4673-a3e2-0403cd692518" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_2b2eee02-092e-4673-a3e2-0403cd692518_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_2b2eee02-092e-4673-a3e2-0403cd692518" xlink:to="loc_dei_EntityDomain_2b2eee02-092e-4673-a3e2-0403cd692518_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3c843d7f-57cc-46d3-b7d4-75f8cc03a244" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_2b2eee02-092e-4673-a3e2-0403cd692518" xlink:to="loc_dei_EntityDomain_3c843d7f-57cc-46d3-b7d4-75f8cc03a244" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_377d6f76-56df-4f7b-b9a7-fccaf808acec" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3c843d7f-57cc-46d3-b7d4-75f8cc03a244" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_377d6f76-56df-4f7b-b9a7-fccaf808acec" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="aat-20200331.xsd#ConsolidatedBalanceSheetsParenthetical"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" id="idd2b9533665c409ca3f4b62e4602b6de_ConsolidatedBalanceSheetsParenthetical">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_86942852-4da7-4091-a58e-0f2ea19996c7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_86942852-4da7-4091-a58e-0f2ea19996c7" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_9d4f2525-b306-48d9-912f-0dbbfd39ab70" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_9d4f2525-b306-48d9-912f-0dbbfd39ab70" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_e23f0179-2515-4d95-8ad0-36022e32db26" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_e23f0179-2515-4d95-8ad0-36022e32db26" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_4d5b113f-3aed-4825-b137-bd03e263212d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_CommonStockSharesIssued_4d5b113f-3aed-4825-b137-bd03e263212d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_33e56c4c-aab3-47e4-9d74-23ec1e633be0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsIssued"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_33e56c4c-aab3-47e4-9d74-23ec1e633be0" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_7ee22028-6b52-425c-9d98-acf43f79a7e9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_7ee22028-6b52-425c-9d98-acf43f79a7e9" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccountUnitsIssued_05486b37-8605-47fb-a3c6-9e4bf7e0ad19" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralPartnersCapitalAccountUnitsIssued"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccountUnitsIssued_05486b37-8605-47fb-a3c6-9e4bf7e0ad19" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_76b23787-a28a-4af9-9cd6-038db8cd0329" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_76b23787-a28a-4af9-9cd6-038db8cd0329" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_fe63be31-f460-4d4f-89e1-f66ba6035d00" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_2c6a1815-4b5c-470c-91fd-71a5c900e85f" xlink:to="loc_us-gaap_StatementTable_fe63be31-f460-4d4f-89e1-f66ba6035d00" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_797c812d-2a5c-4794-b5af-9c2007620b60" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_fe63be31-f460-4d4f-89e1-f66ba6035d00" xlink:to="loc_dei_LegalEntityAxis_797c812d-2a5c-4794-b5af-9c2007620b60" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_797c812d-2a5c-4794-b5af-9c2007620b60_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_797c812d-2a5c-4794-b5af-9c2007620b60" xlink:to="loc_dei_EntityDomain_797c812d-2a5c-4794-b5af-9c2007620b60_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_51c4204b-7fb5-4dcd-a528-4b45cdbc7304" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_797c812d-2a5c-4794-b5af-9c2007620b60" xlink:to="loc_dei_EntityDomain_51c4204b-7fb5-4dcd-a528-4b45cdbc7304" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_5667f214-b6b4-48ee-bc6e-1be92fb8579a" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_51c4204b-7fb5-4dcd-a528-4b45cdbc7304" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_5667f214-b6b4-48ee-bc6e-1be92fb8579a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_fe63be31-f460-4d4f-89e1-f66ba6035d00" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71" xlink:to="loc_us-gaap_EquityComponentDomain_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_716913a2-7674-46ff-aab7-a8bd0c5e0744" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6214c8a9-e0bd-4e6d-839b-c4c67c28fe71" xlink:to="loc_us-gaap_EquityComponentDomain_716913a2-7674-46ff-aab7-a8bd0c5e0744" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_d1f3662f-35f3-40d8-8a47-3cbf92dabb43" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_716913a2-7674-46ff-aab7-a8bd0c5e0744" xlink:to="loc_us-gaap_CommonStockMember_d1f3662f-35f3-40d8-8a47-3cbf92dabb43" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/ConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="simple" xlink:href="aat-20200331.xsd#ConsolidatedStatementsofComprehensiveIncomeUnaudited"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="extended" id="id7d9625e580b47e2a215cc2a55c4d66c_ConsolidatedStatementsofComprehensiveIncomeUnaudited">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_93d3b217-7ae3-4f4f-9c3d-f49edc18a920" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_RevenuesAbstract_93d3b217-7ae3-4f4f-9c3d-f49edc18a920" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_89e2383c-90dc-4f61-80d1-7db07c69c280" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_93d3b217-7ae3-4f4f-9c3d-f49edc18a920" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_89e2383c-90dc-4f61-80d1-7db07c69c280" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncome_529b097a-e9bb-48a9-9a1c-686e991066eb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherOperatingIncome"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_93d3b217-7ae3-4f4f-9c3d-f49edc18a920" xlink:to="loc_us-gaap_OtherOperatingIncome_529b097a-e9bb-48a9-9a1c-686e991066eb" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_bde1252b-4f47-4476-b8b0-4a23ea1bc27d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_93d3b217-7ae3-4f4f-9c3d-f49edc18a920" xlink:to="loc_us-gaap_Revenues_bde1252b-4f47-4476-b8b0-4a23ea1bc27d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingCostsAndExpensesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfOtherPropertyOperatingExpense_1f7a3027-cc31-4f86-acf6-9a086e870057" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfOtherPropertyOperatingExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:to="loc_us-gaap_CostOfOtherPropertyOperatingExpense_1f7a3027-cc31-4f86-acf6-9a086e870057" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateTaxExpense_266976df-7bfd-4a60-a4fa-6bf65fa3357d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateTaxExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:to="loc_us-gaap_RealEstateTaxExpense_266976df-7bfd-4a60-a4fa-6bf65fa3357d" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_1e4c63da-d63f-4735-82d7-e20f1d960ce4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_1e4c63da-d63f-4735-82d7-e20f1d960ce4" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_21e8a9cd-651a-40c4-8ad5-604f59aa42ca" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationAndAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:to="loc_us-gaap_DepreciationAndAmortization_21e8a9cd-651a-40c4-8ad5-604f59aa42ca" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_eeadb6d2-64e4-4370-be4b-56adfb4cb3d2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingExpenses"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingCostsAndExpensesAbstract_ae84876d-854d-4ada-ac81-ff7a1707a008" xlink:to="loc_us-gaap_OperatingExpenses_eeadb6d2-64e4-4370-be4b-56adfb4cb3d2" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_056c4e17-dafd-47c5-becd-6e48351a94b5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_OperatingIncomeLoss_056c4e17-dafd-47c5-becd-6e48351a94b5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_2064befa-5609-4799-95b8-89064d881cf1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_InterestExpense_2064befa-5609-4799-95b8-89064d881cf1" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_c9c5e965-1f29-47d5-84f9-a6e0dfd153ec" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_c9c5e965-1f29-47d5-84f9-a6e0dfd153ec" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_7539d91e-32b6-428f-a3f2-87018e44ff52" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_ProfitLoss_7539d91e-32b6-428f-a3f2-87018e44ff52" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_NetIncomeAttributableToRestrictedShare_7f8ce6b0-765b-4a53-b321-efb7fef10647" xlink:href="aat-20200331.xsd#aat_NetIncomeAttributableToRestrictedShare"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_aat_NetIncomeAttributableToRestrictedShare_7f8ce6b0-765b-4a53-b321-efb7fef10647" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_27002a86-293d-4e44-bd8c-dcfe52ce146e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_27002a86-293d-4e44-bd8c-dcfe52ce146e" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_75395b7a-c0d7-4697-9573-557671206aa0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_NetIncomeLoss_75395b7a-c0d7-4697-9573-557671206aa0" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_c124d07b-59a7-4fd5-a4bd-eedcd156e442" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_c124d07b-59a7-4fd5-a4bd-eedcd156e442" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_39cb725c-e290-46f3-8eb2-282f016f92de" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_c124d07b-59a7-4fd5-a4bd-eedcd156e442" xlink:to="loc_us-gaap_EarningsPerShareBasic_39cb725c-e290-46f3-8eb2-282f016f92de" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_a10745fe-e752-4419-a3ae-c20145215a18" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_c124d07b-59a7-4fd5-a4bd-eedcd156e442" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_a10745fe-e752-4419-a3ae-c20145215a18" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_1f30be7f-8b91-4022-9583-c13ae8f329e1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_1f30be7f-8b91-4022-9583-c13ae8f329e1" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_401f377a-85f6-4e3d-abd3-b9f77404b3bc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_1f30be7f-8b91-4022-9583-c13ae8f329e1" xlink:to="loc_us-gaap_EarningsPerShareDiluted_401f377a-85f6-4e3d-abd3-b9f77404b3bc" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_83f375a3-b57a-4de3-8863-398fc039ee7c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_1f30be7f-8b91-4022-9583-c13ae8f329e1" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_83f375a3-b57a-4de3-8863-398fc039ee7c" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_d1530e06-6c38-49ae-9c97-e773c8e2139d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_d1530e06-6c38-49ae-9c97-e773c8e2139d" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionsPerLimitedPartnershipAndGeneralPartnershipUnitOutstandingBasic_bca03642-ef9c-40ce-94e4-b775c4017e52" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DistributionsPerLimitedPartnershipAndGeneralPartnershipUnitOutstandingBasic"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_DistributionsPerLimitedPartnershipAndGeneralPartnershipUnitOutstandingBasic_bca03642-ef9c-40ce-94e4-b775c4017e52" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_a0759549-6179-4715-a2e6-2651b6289f6e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_6b9d6200-cd34-43ea-8049-27c7de5cd317" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_6b9d6200-cd34-43ea-8049-27c7de5cd317" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_bf2f0e27-7c9d-4c2c-917e-51e657e89ba3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_bf2f0e27-7c9d-4c2c-917e-51e657e89ba3" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_938395d7-ae98-427c-a880-1d92f0363d6d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_938395d7-ae98-427c-a880-1d92f0363d6d" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_e93fb877-ef27-4efa-ab4b-233ffef5e272" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_e93fb877-ef27-4efa-ab4b-233ffef5e272" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_9b11890a-b96f-431a-a6c1-bb39a05b2e83" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_03979fb3-d8ec-461a-aaff-6f671c4110b6" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_9b11890a-b96f-431a-a6c1-bb39a05b2e83" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_ab5bdbf3-3983-48b1-b6db-a266c15b467c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e9725595-cf09-4bd7-af33-857c2e9babe3" xlink:to="loc_us-gaap_StatementTable_ab5bdbf3-3983-48b1-b6db-a266c15b467c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_41c09a49-95ab-4802-b8cf-8d3243637d63" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ab5bdbf3-3983-48b1-b6db-a266c15b467c" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_41c09a49-95ab-4802-b8cf-8d3243637d63" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_41c09a49-95ab-4802-b8cf-8d3243637d63_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_41c09a49-95ab-4802-b8cf-8d3243637d63" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_41c09a49-95ab-4802-b8cf-8d3243637d63_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_635df05a-b5a8-41ec-b02b-7bec6affd6c5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_41c09a49-95ab-4802-b8cf-8d3243637d63" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_635df05a-b5a8-41ec-b02b-7bec6affd6c5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_95e8eca0-c050-49c2-afce-ff8a1d49a13e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateSwapMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_635df05a-b5a8-41ec-b02b-7bec6affd6c5" xlink:to="loc_us-gaap_InterestRateSwapMember_95e8eca0-c050-49c2-afce-ff8a1d49a13e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_1dcd0d10-da6a-4057-95c6-717e720e5481" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForwardContractsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_635df05a-b5a8-41ec-b02b-7bec6affd6c5" xlink:to="loc_us-gaap_ForwardContractsMember_1dcd0d10-da6a-4057-95c6-717e720e5481" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_360b9d94-2196-4ffb-b02b-cca3c1b0926a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ab5bdbf3-3983-48b1-b6db-a266c15b467c" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_360b9d94-2196-4ffb-b02b-cca3c1b0926a" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_360b9d94-2196-4ffb-b02b-cca3c1b0926a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_360b9d94-2196-4ffb-b02b-cca3c1b0926a" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_360b9d94-2196-4ffb-b02b-cca3c1b0926a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6510a362-b5d6-4dad-957c-98475d183693" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_360b9d94-2196-4ffb-b02b-cca3c1b0926a" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6510a362-b5d6-4dad-957c-98475d183693" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_688dad5e-1157-406c-9f3d-903edc935cff" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6510a362-b5d6-4dad-957c-98475d183693" xlink:to="loc_us-gaap_LimitedPartnerMember_688dad5e-1157-406c-9f3d-903edc935cff" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_fadb51af-0859-476d-b491-9b3c245274f6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralPartnerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6510a362-b5d6-4dad-957c-98475d183693" xlink:to="loc_us-gaap_GeneralPartnerMember_fadb51af-0859-476d-b491-9b3c245274f6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_326c4c3a-7975-4aad-be46-217f3f6fa088" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ab5bdbf3-3983-48b1-b6db-a266c15b467c" xlink:to="loc_dei_LegalEntityAxis_326c4c3a-7975-4aad-be46-217f3f6fa088" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_326c4c3a-7975-4aad-be46-217f3f6fa088_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_326c4c3a-7975-4aad-be46-217f3f6fa088" xlink:to="loc_dei_EntityDomain_326c4c3a-7975-4aad-be46-217f3f6fa088_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_6d3ad41f-b426-47bc-ab8e-cc44dd48655c" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_326c4c3a-7975-4aad-be46-217f3f6fa088" xlink:to="loc_dei_EntityDomain_6d3ad41f-b426-47bc-ab8e-cc44dd48655c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_37725339-78e2-4770-a193-80ea70adc661" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_6d3ad41f-b426-47bc-ab8e-cc44dd48655c" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_37725339-78e2-4770-a193-80ea70adc661" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/ConsolidatedStatementofEquityUnaudited" xlink:type="simple" xlink:href="aat-20200331.xsd#ConsolidatedStatementofEquityUnaudited"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ConsolidatedStatementofEquityUnaudited" xlink:type="extended" id="i682046ccc8f14fe58ffe1b5676427f58_ConsolidatedStatementofEquityUnaudited">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a2005946-143c-4b81-813c-2bfc5fbb23c0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a2005946-143c-4b81-813c-2bfc5fbb23c0" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_10332471-bddc-46fc-8551-b892828b2dae" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_10332471-bddc-46fc-8551-b892828b2dae" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0d6b6936-8b13-4f68-9e57-d0a5eead6f43" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0d6b6936-8b13-4f68-9e57-d0a5eead6f43" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_a176c6f4-9c34-4305-837e-57441214bc0e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_ProfitLoss_a176c6f4-9c34-4305-837e-57441214bc0e" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_84dd2145-44c8-41f6-8c44-9e343e4381b6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_84dd2145-44c8-41f6-8c44-9e343e4381b6" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_7cfc8ec2-68ce-469c-a5b2-774bbe2cde03" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_7cfc8ec2-68ce-469c-a5b2-774bbe2cde03" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeited_f1e7f7d8-c7d9-42ed-9721-353c1c10d094" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeited"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeited_f1e7f7d8-c7d9-42ed-9721-353c1c10d094" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_747d8ecc-57de-4333-8885-aa9003e23910" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_747d8ecc-57de-4333-8885-aa9003e23910" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_7a3d75f1-3581-4283-ad41-65bee34ffac8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Dividends"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_Dividends_7a3d75f1-3581-4283-ad41-65bee34ffac8" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_d571f49a-3914-4986-a768-9d9f38e43715" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_d571f49a-3914-4986-a768-9d9f38e43715" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e8f83d5a-7b36-478d-9220-77442f69b64d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e8f83d5a-7b36-478d-9220-77442f69b64d" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_c030da0b-eb41-45cd-b800-3a47653c2eeb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_c030da0b-eb41-45cd-b800-3a47653c2eeb" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_40a25ada-c37c-4ebe-815d-ae234e119be6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_194c80eb-1a32-4de2-978b-ed9026e0cd30" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_40a25ada-c37c-4ebe-815d-ae234e119be6" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_6bc9f333-c173-4fd9-88f0-960fe4563e8a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f0140584-e542-4fb3-b75f-25d6b5a0114a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInPartnersCapitalRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a2005946-143c-4b81-813c-2bfc5fbb23c0" xlink:to="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnits_243bb616-d81e-411c-ab7b-20e43fcc691c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountUnits"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapitalAccountUnits_243bb616-d81e-411c-ab7b-20e43fcc691c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_21a4bb4a-a88c-4fb7-90b9-e2dca6638c6c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapital"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapital_21a4bb4a-a88c-4fb7-90b9-e2dca6638c6c" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_c57a78f7-7afc-4f10-a8f6-f4377b5d008d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsContributed_8fad3151-7e0e-4292-ab79-cc2eed7f8c50" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountUnitsContributed"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsContributed_8fad3151-7e0e-4292-ab79-cc2eed7f8c50" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountContributions_d51477be-0eb9-4d88-9865-df8357b28451" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountContributions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapitalAccountContributions_d51477be-0eb9-4d88-9865-df8357b28451" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PartnersCapitalAccountRestrictedUnitsForfeiture_c04d8d90-b8b4-4004-89ba-bda15dad2cad" xlink:href="aat-20200331.xsd#aat_PartnersCapitalAccountRestrictedUnitsForfeiture"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_aat_PartnersCapitalAccountRestrictedUnitsForfeiture_c04d8d90-b8b4-4004-89ba-bda15dad2cad" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountDistributions_6c459379-97f9-41f6-962b-1627953f4b97" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountDistributions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapitalAccountDistributions_6c459379-97f9-41f6-962b-1627953f4b97" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitBasedCompensation_1c7f6b95-9681-4836-8e12-d7ca5e2f73ee" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountUnitBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_a0c717f7-9e99-47f5-97ac-94fe857777b7" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitBasedCompensation_1c7f6b95-9681-4836-8e12-d7ca5e2f73ee" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_f44fccb6-6bc9-4e2f-8331-0726e6b7ff1c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_3fb07bc4-f4e4-43e0-a198-5ac998f54101" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnits_1b8e8c6b-3b8b-4e61-a1f4-bbe9a3eeb974" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapitalAccountUnits"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_a16c7172-294f-49d3-be0a-c3e790568bdc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnersCapital"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a2005946-143c-4b81-813c-2bfc5fbb23c0" xlink:to="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_d61e9e30-3e86-434a-9947-633499154139" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_d61e9e30-3e86-434a-9947-633499154139" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d61e9e30-3e86-434a-9947-633499154139_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d61e9e30-3e86-434a-9947-633499154139" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d61e9e30-3e86-434a-9947-633499154139_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_703e9cee-6160-4b63-a440-03cec27038b7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_d61e9e30-3e86-434a-9947-633499154139" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_703e9cee-6160-4b63-a440-03cec27038b7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SwapMember_d2ddf265-5f03-4602-b287-a31b6087fcb0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SwapMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_703e9cee-6160-4b63-a440-03cec27038b7" xlink:to="loc_us-gaap_SwapMember_d2ddf265-5f03-4602-b287-a31b6087fcb0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_3d5466bc-046f-4303-bca6-eefe9037e330" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForwardContractsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_703e9cee-6160-4b63-a440-03cec27038b7" xlink:to="loc_us-gaap_ForwardContractsMember_3d5466bc-046f-4303-bca6-eefe9037e330" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_8ac3763a-26f0-484b-96e4-3ccbf59f621c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_8ac3763a-26f0-484b-96e4-3ccbf59f621c" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_8ac3763a-26f0-484b-96e4-3ccbf59f621c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8ac3763a-26f0-484b-96e4-3ccbf59f621c" xlink:to="loc_us-gaap_EquityComponentDomain_8ac3763a-26f0-484b-96e4-3ccbf59f621c_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_8ac3763a-26f0-484b-96e4-3ccbf59f621c" xlink:to="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_e9b252e4-e1f4-4cb6-8301-0456a4d3030a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:to="loc_us-gaap_CommonStockMember_e9b252e4-e1f4-4cb6-8301-0456a4d3030a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_62bb14dd-b0a6-4791-8f84-31a1db1af2af" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_62bb14dd-b0a6-4791-8f84-31a1db1af2af" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b9330c03-747e-4f4c-b3a5-094f4f306683" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:to="loc_us-gaap_RetainedEarningsMember_b9330c03-747e-4f4c-b3a5-094f4f306683" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b07e5b77-905d-4d0e-b25b-c78f972281a8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b07e5b77-905d-4d0e-b25b-c78f972281a8" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_6ead8c47-f1bf-4c49-b9d9-19d9c9e49a82" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_999b11fb-ce73-4218-982f-270ab942114c" xlink:to="loc_us-gaap_NoncontrollingInterestMember_6ead8c47-f1bf-4c49-b9d9-19d9c9e49a82" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_25a7f289-0aa9-4afa-bba6-b32a346cf958" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:to="loc_dei_LegalEntityAxis_25a7f289-0aa9-4afa-bba6-b32a346cf958" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_25a7f289-0aa9-4afa-bba6-b32a346cf958_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_25a7f289-0aa9-4afa-bba6-b32a346cf958" xlink:to="loc_dei_EntityDomain_25a7f289-0aa9-4afa-bba6-b32a346cf958_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3cd7582e-9a84-425a-a136-ec28a7b37ec1" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_25a7f289-0aa9-4afa-bba6-b32a346cf958" xlink:to="loc_dei_EntityDomain_3cd7582e-9a84-425a-a136-ec28a7b37ec1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_bcc81cc2-4ba5-435f-8e96-9c2b45532596" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3cd7582e-9a84-425a-a136-ec28a7b37ec1" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_bcc81cc2-4ba5-435f-8e96-9c2b45532596" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a2929467-160c-4f82-b860-ce87a219f102" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_cf39408d-5bcf-4d32-a0f7-0a0e3bf21f91" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a2929467-160c-4f82-b860-ce87a219f102" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_e1999a50-4c94-4d79-aa29-9e29eefd5ada" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a2929467-160c-4f82-b860-ce87a219f102" xlink:to="loc_us-gaap_LimitedPartnerMember_e1999a50-4c94-4d79-aa29-9e29eefd5ada" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_c015348f-41e0-48de-acde-439279310338" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GeneralPartnerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a2929467-160c-4f82-b860-ce87a219f102" xlink:to="loc_us-gaap_GeneralPartnerMember_c015348f-41e0-48de-acde-439279310338" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerCapitalComponentsAxis_83ee800e-162a-4754-823b-e3c901ef7283" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerCapitalComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_eb3d387f-181d-46d4-9c51-5b411273720e" xlink:to="loc_us-gaap_PartnerCapitalComponentsAxis_83ee800e-162a-4754-823b-e3c901ef7283" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerCapitalComponentsDomain_83ee800e-162a-4754-823b-e3c901ef7283_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerCapitalComponentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerCapitalComponentsAxis_83ee800e-162a-4754-823b-e3c901ef7283" xlink:to="loc_us-gaap_PartnerCapitalComponentsDomain_83ee800e-162a-4754-823b-e3c901ef7283_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerCapitalComponentsDomain_daa5b2c4-f0de-44ca-b4a6-cb6b8db197a1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerCapitalComponentsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerCapitalComponentsAxis_83ee800e-162a-4754-823b-e3c901ef7283" xlink:to="loc_us-gaap_PartnerCapitalComponentsDomain_daa5b2c4-f0de-44ca-b4a6-cb6b8db197a1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_38f4d714-2011-489d-8c0d-449e931089fd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerCapitalComponentsDomain_daa5b2c4-f0de-44ca-b4a6-cb6b8db197a1" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_38f4d714-2011-489d-8c0d-449e931089fd" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="aat-20200331.xsd#ConsolidatedStatementsofCashFlowsUnaudited"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended" id="i1a6c33d6d8a34b20a73a49e77237834e_ConsolidatedStatementsofCashFlowsUnaudited">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_1421e0a2-7bbd-4f05-91a8-5218241d377c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_1421e0a2-7bbd-4f05-91a8-5218241d377c" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_00989542-10d1-4b7e-889f-e8c7d86e1c0f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_1421e0a2-7bbd-4f05-91a8-5218241d377c" xlink:to="loc_us-gaap_ProfitLoss_00989542-10d1-4b7e-889f-e8c7d86e1c0f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_1421e0a2-7bbd-4f05-91a8-5218241d377c" xlink:to="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DeferredRentRevenueAndAmortizationOfLeaseIntangibles_10789e6c-2d97-4935-b1e7-00c1c53f1d6f" xlink:href="aat-20200331.xsd#aat_DeferredRentRevenueAndAmortizationOfLeaseIntangibles"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_aat_DeferredRentRevenueAndAmortizationOfLeaseIntangibles_10789e6c-2d97-4935-b1e7-00c1c53f1d6f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_9a5b5e71-7560-4611-b23f-d691a5f13291" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_9a5b5e71-7560-4611-b23f-d691a5f13291" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmortizationOfDebtIssuanceCostsAndDebtFairValueAdjustments_1e247fda-9441-470d-a4da-dab71ab9a8ad" xlink:href="aat-20200331.xsd#aat_AmortizationOfDebtIssuanceCostsAndDebtFairValueAdjustments"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_aat_AmortizationOfDebtIssuanceCostsAndDebtFairValueAdjustments_1e247fda-9441-470d-a4da-dab71ab9a8ad" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_cbfd7df6-cbb5-44d4-873b-c9b0157267ab" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensation"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_us-gaap_ShareBasedCompensation_cbfd7df6-cbb5-44d4-873b-c9b0157267ab" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnTerminationOfLease_1f64eb17-c6b6-43b0-84dc-4b23bfd50286" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainLossOnTerminationOfLease"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_us-gaap_GainLossOnTerminationOfLease_1f64eb17-c6b6-43b0-84dc-4b23bfd50286" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OtherNoncashInterestExpense_13abc465-ae57-42b8-b525-11e7213ecf6a" xlink:href="aat-20200331.xsd#aat_OtherNoncashInterestExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_aat_OtherNoncashInterestExpense_13abc465-ae57-42b8-b525-11e7213ecf6a" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_e93d9107-6fe8-44de-96ad-a06320bd79a4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoncashIncomeExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_e93d9107-6fe8-44de-96ad-a06320bd79a4" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_3b20eef8-e196-42a2-a875-e148c75761f2" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_94331b9e-b820-45c3-800f-5341e5b028cc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_94331b9e-b820-45c3-800f-5341e5b028cc" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_bea2342c-11cc-4e9c-a7ea-7eff594aeae5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_bea2342c-11cc-4e9c-a7ea-7eff594aeae5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_94598667-074c-4f21-8864-399f130f08fc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_94598667-074c-4f21-8864-399f130f08fc" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_IncreaseDecreaseinSecurityDepositsPayable_63d2213b-285e-4184-aec6-4539c50806a3" xlink:href="aat-20200331.xsd#aat_IncreaseDecreaseinSecurityDepositsPayable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:to="loc_aat_IncreaseDecreaseinSecurityDepositsPayable_63d2213b-285e-4184-aec6-4539c50806a3" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherDeferredLiability_2e9dcead-95ff-4e97-8c23-ef9ad7b82803" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInOtherDeferredLiability"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_88595d4b-ce85-4f01-a32b-c63507106bd4" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherDeferredLiability_2e9dcead-95ff-4e97-8c23-ef9ad7b82803" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b6de3337-e404-457a-b502-639d905b1cf8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_1421e0a2-7bbd-4f05-91a8-5218241d377c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b6de3337-e404-457a-b502-639d905b1cf8" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_b7cb4e90-9b4c-4700-8947-f5c68f8c6e90" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_b7cb4e90-9b4c-4700-8947-f5c68f8c6e90" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForCapitalImprovements_22ab3bc2-24b1-4cbd-8d0f-fbccb6108821" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsForCapitalImprovements"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_b7cb4e90-9b4c-4700-8947-f5c68f8c6e90" xlink:to="loc_us-gaap_PaymentsForCapitalImprovements_22ab3bc2-24b1-4cbd-8d0f-fbccb6108821" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInLeaseAcquisitionCosts_5a3c773f-b41e-455c-9004-9fda4e4895a7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInLeaseAcquisitionCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_b7cb4e90-9b4c-4700-8947-f5c68f8c6e90" xlink:to="loc_us-gaap_IncreaseDecreaseInLeaseAcquisitionCosts_5a3c773f-b41e-455c-9004-9fda4e4895a7" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_91fb4a85-bb11-4747-bcdf-62477eec3866" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_b7cb4e90-9b4c-4700-8947-f5c68f8c6e90" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_91fb4a85-bb11-4747-bcdf-62477eec3866" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfSecuredDebt_3fcca025-842c-45e4-a38e-0df183755e02" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RepaymentsOfSecuredDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_RepaymentsOfSecuredDebt_3fcca025-842c-45e4-a38e-0df183755e02" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromUnsecuredLinesOfCredit_a7c1290d-15d2-4614-98bb-7cfdfc745ab5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromUnsecuredLinesOfCredit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_ProceedsFromUnsecuredLinesOfCredit_a7c1290d-15d2-4614-98bb-7cfdfc745ab5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_eff0e1fb-eac9-4ed1-bbd6-194d9936c34f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_eff0e1fb-eac9-4ed1-bbd6-194d9936c34f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_8ce6dd58-3f09-40b8-a629-840abd811f7f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_8ce6dd58-3f09-40b8-a629-840abd811f7f" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPartnershipContribution_2bb11c8d-3f8f-482a-ab6c-e8e63405346f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromPartnershipContribution"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_ProceedsFromPartnershipContribution_2bb11c8d-3f8f-482a-ab6c-e8e63405346f" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_6380c938-6c66-485e-b65d-412f7566bded" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsOfDividends"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_PaymentsOfDividends_6380c938-6c66-485e-b65d-412f7566bded" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_58763817-c891-4425-af45-5d1ff53614d8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1af2fb32-32aa-42a5-8634-25e9330e5cd4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_58763817-c891-4425-af45-5d1ff53614d8" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_7cd6db09-94c6-455a-a618-ef62c83243a2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_7cd6db09-94c6-455a-a618-ef62c83243a2" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_3ff4f70e-c847-42e2-b811-19d19f3d4c63" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_3ff4f70e-c847-42e2-b811-19d19f3d4c63" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_38092253-bf7a-4ee5-833f-9fdb3250562f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_f0232999-5962-423d-af79-45246ee6d5a2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_f0232999-5962-423d-af79-45246ee6d5a2" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_bb598c87-eae5-41c9-a563-ca059eabd52f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_bb598c87-eae5-41c9-a563-ca059eabd52f" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_ea0db487-db09-449e-bbe7-070f9918766d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_5ac23778-d1b2-4e3a-b275-09c89e7c3cad" xlink:to="loc_us-gaap_StatementTable_ea0db487-db09-449e-bbe7-070f9918766d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_597877c4-2d1a-40c0-99a6-5adc57855f30" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ea0db487-db09-449e-bbe7-070f9918766d" xlink:to="loc_dei_LegalEntityAxis_597877c4-2d1a-40c0-99a6-5adc57855f30" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_597877c4-2d1a-40c0-99a6-5adc57855f30_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_597877c4-2d1a-40c0-99a6-5adc57855f30" xlink:to="loc_dei_EntityDomain_597877c4-2d1a-40c0-99a6-5adc57855f30_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_ca4c74ce-a5dc-4ee4-8111-43f0a0d081ee" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_597877c4-2d1a-40c0-99a6-5adc57855f30" xlink:to="loc_dei_EntityDomain_ca4c74ce-a5dc-4ee4-8111-43f0a0d081ee" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_048c3f8f-7d95-49c6-890e-0e72a9eff982" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_ca4c74ce-a5dc-4ee4-8111-43f0a0d081ee" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_048c3f8f-7d95-49c6-890e-0e72a9eff982" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES" xlink:type="simple" xlink:href="aat-20200331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES" xlink:type="extended" id="ibffb801899354d1cb8f3a08355debaad_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies" xlink:type="simple" xlink:href="aat-20200331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies" xlink:type="extended" id="iedfc0876b7864835b2841099503d48d0_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables" xlink:type="simple" xlink:href="aat-20200331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables" xlink:type="extended" id="i5505a9c70bc74892b36afcc6c7ba14f9_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="extended" id="ie0e90d04097d43878ba01e2ee7cba1aa_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSupplementDisclosuresRelatedtoConsolidatedStatementsofCashFlowsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSupplementDisclosuresRelatedtoConsolidatedStatementsofCashFlowsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSupplementDisclosuresRelatedtoConsolidatedStatementsofCashFlowsDetails" xlink:type="extended" id="if5a49f6c3aa747deb3829d5db4525319_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESSupplementDisclosuresRelatedtoConsolidatedStatementsofCashFlowsDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASES" xlink:type="simple" xlink:href="aat-20200331.xsd#ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASES" xlink:type="extended" id="i4ac1b0ef7286465fb1f3b54a2eed1a6d_ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESTables" xlink:type="simple" xlink:href="aat-20200331.xsd#ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESTables" xlink:type="extended" id="i1c5ea56468cc48c493cd5f56cc3c1a32_ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESAcquiredLeaseIntangiblesandLeasingCostsIncludedinOtherAssetsandOtherLiabilitiesandDeferredCreditsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESAcquiredLeaseIntangiblesandLeasingCostsIncludedinOtherAssetsandOtherLiabilitiesandDeferredCreditsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESAcquiredLeaseIntangiblesandLeasingCostsIncludedinOtherAssetsandOtherLiabilitiesandDeferredCreditsDetails" xlink:type="extended" id="iacb78a303e344c10af1bc6ad892f6757_ACQUIREDINPLACELEASESANDABOVEBELOWMARKETLEASESAcquiredLeaseIntangiblesandLeasingCostsIncludedinOtherAssetsandOtherLiabilitiesandDeferredCreditsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetOffMarketLeaseFavorableGross_f2c5bb88-b3e0-48c1-a67e-55a554cb09d4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetOffMarketLeaseFavorableGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetOffMarketLeaseFavorableGross_f2c5bb88-b3e0-48c1-a67e-55a554cb09d4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_bef6d577-19e9-48ca-b4db-ab00b56bd57d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_bef6d577-19e9-48ca-b4db-ab00b56bd57d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c94b0868-ae5f-4e1e-b1fa-0bb9265bf6f4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c94b0868-ae5f-4e1e-b1fa-0bb9265bf6f4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseGross_aebc1d13-583f-4bf7-b67e-fdcfe8786816" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BelowMarketLeaseGross"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_BelowMarketLeaseGross_aebc1d13-583f-4bf7-b67e-fdcfe8786816" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseAccumulatedAmortization_17f78ad6-54a5-4377-9428-8df84f49385c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BelowMarketLeaseAccumulatedAmortization"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_BelowMarketLeaseAccumulatedAmortization_17f78ad6-54a5-4377-9428-8df84f49385c" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BelowMarketLeaseNet_f956ceb7-b9bf-4c54-a5e4-b8c03d86318d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BelowMarketLeaseNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_BelowMarketLeaseNet_f956ceb7-b9bf-4c54-a5e4-b8c03d86318d" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_07a080ff-0e9f-4463-9ff8-76718a3aafea" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2db0d647-787d-4880-b8f3-1ed54bdbd4ff" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_07a080ff-0e9f-4463-9ff8-76718a3aafea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_58011ddd-c0b0-40e9-97f1-68de3d1e89ac" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_07a080ff-0e9f-4463-9ff8-76718a3aafea" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_58011ddd-c0b0-40e9-97f1-68de3d1e89ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58011ddd-c0b0-40e9-97f1-68de3d1e89ac_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_58011ddd-c0b0-40e9-97f1-68de3d1e89ac" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_58011ddd-c0b0-40e9-97f1-68de3d1e89ac_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c349ebc-c93e-468e-a556-697f8de16b00" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_58011ddd-c0b0-40e9-97f1-68de3d1e89ac" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c349ebc-c93e-468e-a556-697f8de16b00" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseAgreementsMember_759018dc-5ba1-476c-ae49-8e2559284988" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeaseAgreementsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c349ebc-c93e-468e-a556-697f8de16b00" xlink:to="loc_us-gaap_LeaseAgreementsMember_759018dc-5ba1-476c-ae49-8e2559284988" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAcquiredInPlaceMember_41fe07d0-c148-433e-a898-e959062eaaf4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LeasesAcquiredInPlaceMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseAgreementsMember_759018dc-5ba1-476c-ae49-8e2559284988" xlink:to="loc_us-gaap_LeasesAcquiredInPlaceMember_41fe07d0-c148-433e-a898-e959062eaaf4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AboveMarketLeasesMember_875f35b7-a769-4ccc-aecc-c7d96e1e48fb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AboveMarketLeasesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseAgreementsMember_759018dc-5ba1-476c-ae49-8e2559284988" xlink:to="loc_us-gaap_AboveMarketLeasesMember_875f35b7-a769-4ccc-aecc-c7d96e1e48fb" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTS" xlink:type="simple" xlink:href="aat-20200331.xsd#FAIRVALUEOFFINANCIALINSTRUMENTS"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTS" xlink:type="extended" id="ia6a491449b054679ae642582f944b7c8_FAIRVALUEOFFINANCIALINSTRUMENTS"/>
<link:roleRef roleURI="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSTables" xlink:type="simple" xlink:href="aat-20200331.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSTables" xlink:type="extended" id="i0cf8a1be023f421089a6152f3ddd07c5_FAIRVALUEOFFINANCIALINSTRUMENTSTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSDetails" xlink:type="extended" id="id316c5ab52c940339aba1f2fd1f52284_FAIRVALUEOFFINANCIALINSTRUMENTSDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_dc13b0ae-55cb-48cd-9469-57d55c8879c4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMeasurementInput_3513080e-0420-4d42-b8c3-4b6aa442014c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentMeasurementInput"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_dc13b0ae-55cb-48cd-9469-57d55c8879c4" xlink:to="loc_us-gaap_DebtInstrumentMeasurementInput_3513080e-0420-4d42-b8c3-4b6aa442014c" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_ad79f6f5-6b3e-4a37-b4b1-842e2e833540" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_dc13b0ae-55cb-48cd-9469-57d55c8879c4" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_ad79f6f5-6b3e-4a37-b4b1-842e2e833540" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c996469e-eb59-4ee2-a99e-79d44ccea4b4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_ad79f6f5-6b3e-4a37-b4b1-842e2e833540" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c996469e-eb59-4ee2-a99e-79d44ccea4b4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c996469e-eb59-4ee2-a99e-79d44ccea4b4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c996469e-eb59-4ee2-a99e-79d44ccea4b4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c996469e-eb59-4ee2-a99e-79d44ccea4b4_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_66752898-25a7-4a92-99fd-77334598dd3d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c996469e-eb59-4ee2-a99e-79d44ccea4b4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_66752898-25a7-4a92-99fd-77334598dd3d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_32fc5de1-0a16-42c5-b0e5-4843343c902b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_66752898-25a7-4a92-99fd-77334598dd3d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_32fc5de1-0a16-42c5-b0e5-4843343c902b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b48b8312-17cf-4681-bea6-02726ac5e125" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_ad79f6f5-6b3e-4a37-b4b1-842e2e833540" xlink:to="loc_srt_RangeAxis_b48b8312-17cf-4681-bea6-02726ac5e125" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b48b8312-17cf-4681-bea6-02726ac5e125_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b48b8312-17cf-4681-bea6-02726ac5e125" xlink:to="loc_srt_RangeMember_b48b8312-17cf-4681-bea6-02726ac5e125_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_932ecb96-4ef5-4271-868d-55aaed12f8d3" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b48b8312-17cf-4681-bea6-02726ac5e125" xlink:to="loc_srt_RangeMember_932ecb96-4ef5-4271-868d-55aaed12f8d3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_f511da8c-8d5a-40b4-b2c6-d1a0c14c4863" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_932ecb96-4ef5-4271-868d-55aaed12f8d3" xlink:to="loc_srt_MinimumMember_f511da8c-8d5a-40b4-b2c6-d1a0c14c4863" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_af2f7632-e559-4417-bf19-90bdaad36345" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_932ecb96-4ef5-4271-868d-55aaed12f8d3" xlink:to="loc_srt_MaximumMember_af2f7632-e559-4417-bf19-90bdaad36345" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSFinancialLiabilitiesFairValueMeasurementonaRecurringBasisDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSFinancialLiabilitiesFairValueMeasurementonaRecurringBasisDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSFinancialLiabilitiesFairValueMeasurementonaRecurringBasisDetails" xlink:type="extended" id="id123525811b44f79843e60f813f979bb_FAIRVALUEOFFINANCIALINSTRUMENTSFinancialLiabilitiesFairValueMeasurementonaRecurringBasisDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_03e80d1e-1632-4796-ba20-7f7d2a176cf2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_3f77809e-06ee-44cd-bf55-05f58bc114e4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_03e80d1e-1632-4796-ba20-7f7d2a176cf2" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_3f77809e-06ee-44cd-bf55-05f58bc114e4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_24610b3b-d917-412b-aec2-34b6c71cabde" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_03e80d1e-1632-4796-ba20-7f7d2a176cf2" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_24610b3b-d917-412b-aec2-34b6c71cabde" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_19c33ea7-2125-4345-b321-7465347f6421" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateDerivativeLiabilitiesAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_03e80d1e-1632-4796-ba20-7f7d2a176cf2" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_19c33ea7-2125-4345-b321-7465347f6421" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_00408705-da01-4599-8530-ef5035e0702d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_03e80d1e-1632-4796-ba20-7f7d2a176cf2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_00408705-da01-4599-8530-ef5035e0702d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6a0df6aa-08a8-40f1-8929-32df3d1c14a4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_00408705-da01-4599-8530-ef5035e0702d" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6a0df6aa-08a8-40f1-8929-32df3d1c14a4" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6a0df6aa-08a8-40f1-8929-32df3d1c14a4_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6a0df6aa-08a8-40f1-8929-32df3d1c14a4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6a0df6aa-08a8-40f1-8929-32df3d1c14a4_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_5c02c5ac-b8e4-4e38-9c36-5fcd136f41b8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_6a0df6aa-08a8-40f1-8929-32df3d1c14a4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_5c02c5ac-b8e4-4e38-9c36-5fcd136f41b8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_a3698f0b-4443-4bf7-857e-0a3566025061" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_5c02c5ac-b8e4-4e38-9c36-5fcd136f41b8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_a3698f0b-4443-4bf7-857e-0a3566025061" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9b9c79db-8f74-48be-acef-db429ba04e14" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_00408705-da01-4599-8530-ef5035e0702d" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9b9c79db-8f74-48be-acef-db429ba04e14" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9b9c79db-8f74-48be-acef-db429ba04e14_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9b9c79db-8f74-48be-acef-db429ba04e14" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9b9c79db-8f74-48be-acef-db429ba04e14_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f44287f3-5f7c-4472-8dc6-6835dae6004d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_9b9c79db-8f74-48be-acef-db429ba04e14" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f44287f3-5f7c-4472-8dc6-6835dae6004d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_faced0cb-c3da-4006-8c11-914e869c5fb9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f44287f3-5f7c-4472-8dc6-6835dae6004d" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_faced0cb-c3da-4006-8c11-914e869c5fb9" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_7ed86441-7864-4bbb-bebb-40b9524ea062" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f44287f3-5f7c-4472-8dc6-6835dae6004d" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_7ed86441-7864-4bbb-bebb-40b9524ea062" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_85979008-a222-491a-aa47-39411334baec" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f44287f3-5f7c-4472-8dc6-6835dae6004d" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_85979008-a222-491a-aa47-39411334baec" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSCarryingAmountandFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSCarryingAmountandFairValueofFinancialInstrumentsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSCarryingAmountandFairValueofFinancialInstrumentsDetails" xlink:type="extended" id="i627bc8d9475a486bbac0463be811e539_FAIRVALUEOFFINANCIALINSTRUMENTSCarryingAmountandFairValueofFinancialInstrumentsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a649d931-3f98-4269-ae25-45faeca6fa7b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_96a36f67-a74a-45b7-91de-79960bc9cde8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a649d931-3f98-4269-ae25-45faeca6fa7b" xlink:to="loc_us-gaap_LongTermDebtFairValue_96a36f67-a74a-45b7-91de-79960bc9cde8" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_f18c9011-0fe3-475c-90e3-228a3e356fa9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_a649d931-3f98-4269-ae25-45faeca6fa7b" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_f18c9011-0fe3-475c-90e3-228a3e356fa9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_f18c9011-0fe3-475c-90e3-228a3e356fa9" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_64915f73-3ebb-4cb4-8f03-6e60217dc743" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_b0fe5190-2a83-4524-bf8a-0c6c01b60dc3" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_64915f73-3ebb-4cb4-8f03-6e60217dc743" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_9f533cd7-3604-415e-9b6b-b9d74a8169a4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_64915f73-3ebb-4cb4-8f03-6e60217dc743" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_9f533cd7-3604-415e-9b6b-b9d74a8169a4" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_f18c9011-0fe3-475c-90e3-228a3e356fa9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_0de4f032-ea9f-4c10-8c9f-9b2ff31d8e9f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_3d2db14a-acf7-442c-8dd6-81ef40b7223d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:to="loc_us-gaap_SecuredDebtMember_3d2db14a-acf7-442c-8dd6-81ef40b7223d" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_c2d3286d-a52a-4961-8333-c831d076cc82" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnsecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:to="loc_us-gaap_UnsecuredDebtMember_c2d3286d-a52a-4961-8333-c831d076cc82" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_fd24e215-89df-4c7a-94fd-6512425174c3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:to="loc_us-gaap_SeniorNotesMember_fd24e215-89df-4c7a-94fd-6512425174c3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_27734612-79fc-4c47-859e-38e163690428" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c638882a-6221-4119-8791-529be7ce3d04" xlink:to="loc_us-gaap_LineOfCreditMember_27734612-79fc-4c47-859e-38e163690428" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_1f23c4fe-d981-408a-93ca-d99be12805e0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_f18c9011-0fe3-475c-90e3-228a3e356fa9" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_1f23c4fe-d981-408a-93ca-d99be12805e0" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1f23c4fe-d981-408a-93ca-d99be12805e0_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_1f23c4fe-d981-408a-93ca-d99be12805e0" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1f23c4fe-d981-408a-93ca-d99be12805e0_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6b50f8b5-9d7c-402a-9b9b-a56bc6a5491a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_1f23c4fe-d981-408a-93ca-d99be12805e0" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6b50f8b5-9d7c-402a-9b9b-a56bc6a5491a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_4df52eab-8c64-418f-9f92-41d8b4f38861" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6b50f8b5-9d7c-402a-9b9b-a56bc6a5491a" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_4df52eab-8c64-418f-9f92-41d8b4f38861" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_b5fc0b6b-9961-4dc1-b767-4e4bda543d1b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_4df52eab-8c64-418f-9f92-41d8b4f38861" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_b5fc0b6b-9961-4dc1-b767-4e4bda543d1b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_f1aaa3d8-5a94-4c4b-a255-507dd9d2918b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_4df52eab-8c64-418f-9f92-41d8b4f38861" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_f1aaa3d8-5a94-4c4b-a255-507dd9d2918b" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIES" xlink:type="simple" xlink:href="aat-20200331.xsd#DERIVATIVEANDHEDGINGACTIVITIES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIES" xlink:type="extended" id="ibc5f2ae09bcb46129c3c652336f05972_DERIVATIVEANDHEDGINGACTIVITIES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIESTables" xlink:type="simple" xlink:href="aat-20200331.xsd#DERIVATIVEANDHEDGINGACTIVITIESTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIESTables" xlink:type="extended" id="ib1a952df775f495a9b4e9c87b4e6abdb_DERIVATIVEANDHEDGINGACTIVITIESTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIESDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#DERIVATIVEANDHEDGINGACTIVITIESDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DERIVATIVEANDHEDGINGACTIVITIESDetails" xlink:type="extended" id="ie111b255b6844ebbaf72876289587a0b_DERIVATIVEANDHEDGINGACTIVITIESDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_11daa147-3a92-4eaf-bd4e-e4a62cb082dc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFixedInterestRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_11daa147-3a92-4eaf-bd4e-e4a62cb082dc" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTermOfContract_9914134e-cd3c-4ca7-a704-7b06844718cf" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeTermOfContract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeTermOfContract_9914134e-cd3c-4ca7-a704-7b06844718cf" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainOnDerivative_4683f2a7-0c34-4bd2-abaf-755e9905ff07" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainOnDerivative"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeGainOnDerivative_4683f2a7-0c34-4bd2-abaf-755e9905ff07" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_431a8499-25e0-4db4-8762-3719deffe0df" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeNotionalAmount_431a8499-25e0-4db4-8762-3719deffe0df" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInceptionDates_264d617b-3b48-4ed9-a881-d65077c25875" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInceptionDates"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeInceptionDates_264d617b-3b48-4ed9-a881-d65077c25875" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMaturityDates_602b3f46-aefb-480b-9ccf-222c1595794e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeMaturityDates"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeMaturityDates_602b3f46-aefb-480b-9ccf-222c1595794e" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_fad2c6c7-ff15-4b17-814d-89e0d1e99241" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateDerivativeLiabilitiesAtFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_fad2c6c7-ff15-4b17-814d-89e0d1e99241" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationPeriodOfDeferredGainLossOnDiscontinuationOfFairValueHedge1_d2720392-126c-4f5a-8dd0-2f0ac56a67a8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationPeriodOfDeferredGainLossOnDiscontinuationOfFairValueHedge1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_AmortizationPeriodOfDeferredGainLossOnDiscontinuationOfFairValueHedge1_d2720392-126c-4f5a-8dd0-2f0ac56a67a8" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths_f84ebfe8-ba66-4e22-94d5-5cfea1fb9d9f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths_f84ebfe8-ba66-4e22-94d5-5cfea1fb9d9f" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_513a973d-b082-423c-ab01-a972b15382bd" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_a5151c43-d46e-4ce8-a83d-9f17c08ee637" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:to="loc_us-gaap_HedgingDesignationAxis_a5151c43-d46e-4ce8-a83d-9f17c08ee637" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a5151c43-d46e-4ce8-a83d-9f17c08ee637_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_a5151c43-d46e-4ce8-a83d-9f17c08ee637" xlink:to="loc_us-gaap_HedgingDesignationDomain_a5151c43-d46e-4ce8-a83d-9f17c08ee637_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_2b3274f6-ba5d-44f8-b0c9-e4235ae3d657" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_a5151c43-d46e-4ce8-a83d-9f17c08ee637" xlink:to="loc_us-gaap_HedgingDesignationDomain_2b3274f6-ba5d-44f8-b0c9-e4235ae3d657" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_77c54cd8-3871-4a2b-a29a-7ec78d13c209" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_2b3274f6-ba5d-44f8-b0c9-e4235ae3d657" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_77c54cd8-3871-4a2b-a29a-7ec78d13c209" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_ae28f0d0-3069-405f-98a6-6b37f3b11b12" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_ae28f0d0-3069-405f-98a6-6b37f3b11b12" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_ae28f0d0-3069-405f-98a6-6b37f3b11b12_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_ae28f0d0-3069-405f-98a6-6b37f3b11b12" xlink:to="loc_us-gaap_HedgingRelationshipDomain_ae28f0d0-3069-405f-98a6-6b37f3b11b12_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_af8cda73-015a-48cf-ba58-f14fee9f5d86" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_ae28f0d0-3069-405f-98a6-6b37f3b11b12" xlink:to="loc_us-gaap_HedgingRelationshipDomain_af8cda73-015a-48cf-ba58-f14fee9f5d86" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_e35547dc-8c08-4624-98cb-065bb37690ae" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashFlowHedgingMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_af8cda73-015a-48cf-ba58-f14fee9f5d86" xlink:to="loc_us-gaap_CashFlowHedgingMember_e35547dc-8c08-4624-98cb-065bb37690ae" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_83c085bd-f9f4-4a5c-80da-41a290e26702" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:to="loc_dei_LegalEntityAxis_83c085bd-f9f4-4a5c-80da-41a290e26702" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_83c085bd-f9f4-4a5c-80da-41a290e26702_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_83c085bd-f9f4-4a5c-80da-41a290e26702" xlink:to="loc_dei_EntityDomain_83c085bd-f9f4-4a5c-80da-41a290e26702_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_bccc043a-8be8-4d25-832f-5555584252a6" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_83c085bd-f9f4-4a5c-80da-41a290e26702" xlink:to="loc_dei_EntityDomain_bccc043a-8be8-4d25-832f-5555584252a6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_c4c750cd-9eb6-4268-96b9-d09433d37d64" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_bccc043a-8be8-4d25-832f-5555584252a6" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_c4c750cd-9eb6-4268-96b9-d09433d37d64" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_dfb1b243-73e1-409e-9204-6cc5d48e5eb1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_dfb1b243-73e1-409e-9204-6cc5d48e5eb1" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_dfb1b243-73e1-409e-9204-6cc5d48e5eb1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_dfb1b243-73e1-409e-9204-6cc5d48e5eb1" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_dfb1b243-73e1-409e-9204-6cc5d48e5eb1_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_dfb1b243-73e1-409e-9204-6cc5d48e5eb1" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_80bfd65f-c49f-4cbb-bb7a-16d7a52b6ed0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForwardContractsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:to="loc_us-gaap_ForwardContractsMember_80bfd65f-c49f-4cbb-bb7a-16d7a52b6ed0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_InterestRateSwap192021Member_f7e5a8cc-0c87-4548-bb1a-32fd1c98da7f" xlink:href="aat-20200331.xsd#aat_InterestRateSwap192021Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:to="loc_aat_InterestRateSwap192021Member_f7e5a8cc-0c87-4548-bb1a-32fd1c98da7f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_InterestRateSwap312023Member_a7685d30-416d-4563-be3c-9b4ef8d3ee93" xlink:href="aat-20200331.xsd#aat_InterestRateSwap312023Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:to="loc_aat_InterestRateSwap312023Member_a7685d30-416d-4563-be3c-9b4ef8d3ee93" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryLockMember_064a9451-64d5-43fd-b876-2e68403d9e0e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryLockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9218e9ed-40c0-45df-8af9-d0356de6520a" xlink:to="loc_us-gaap_TreasuryLockMember_064a9451-64d5-43fd-b876-2e68403d9e0e" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_CounterpartyNameAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_f57e77c9-4c4d-4877-bf32-26bf47a06bea" xlink:to="loc_srt_CounterpartyNameAxis_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_322da968-84c2-4102-8697-55c5e43251ee" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_6ebcc6ff-9893-43b3-b24c-51f95e7c2d47" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_322da968-84c2-4102-8697-55c5e43251ee" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_BankofAmericaN.A.Member_c44c7ffe-c041-4c05-90bb-5bf268a11031" xlink:href="aat-20200331.xsd#aat_BankofAmericaN.A.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_322da968-84c2-4102-8697-55c5e43251ee" xlink:to="loc_aat_BankofAmericaN.A.Member_c44c7ffe-c041-4c05-90bb-5bf268a11031" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_U.S.BankN.A.Member_6df8358f-267e-438b-9948-dec4b03932e8" xlink:href="aat-20200331.xsd#aat_U.S.BankN.A.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_322da968-84c2-4102-8697-55c5e43251ee" xlink:to="loc_aat_U.S.BankN.A.Member_6df8358f-267e-438b-9948-dec4b03932e8" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WellsFargoBankN.A.Member_22c79ba0-20f8-461f-9c1c-fc130db28722" xlink:href="aat-20200331.xsd#aat_WellsFargoBankN.A.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_322da968-84c2-4102-8697-55c5e43251ee" xlink:to="loc_aat_WellsFargoBankN.A.Member_22c79ba0-20f8-461f-9c1c-fc130db28722" xlink:type="arc" order="2"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERASSETS" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERASSETS"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERASSETS" xlink:type="extended" id="i82fed077fd6947dc8df73fedd4c8f326_OTHERASSETS"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERASSETSTables" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERASSETSTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERASSETSTables" xlink:type="extended" id="i29fbfbea93414b4b9d34716e9c09570c_OTHERASSETSTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERASSETSDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERASSETSDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERASSETSDetails" xlink:type="extended" id="i7d4f1474c6004d63908f018846ba6fe9_OTHERASSETSDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITS" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERLIABILITIESANDDEFERREDCREDITS"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITS" xlink:type="extended" id="i39dd1927b42b4af5bbec990436523702_OTHERLIABILITIESANDDEFERREDCREDITS"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITSTables" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERLIABILITIESANDDEFERREDCREDITSTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITSTables" xlink:type="extended" id="i89263d10d9e24724b4a05d405d7535cb_OTHERLIABILITIESANDDEFERREDCREDITSTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITSDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHERLIABILITIESANDDEFERREDCREDITSDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHERLIABILITIESANDDEFERREDCREDITSDetails" xlink:type="extended" id="i0e2523d9a1254da3873a6d349553ba27_OTHERLIABILITIESANDDEFERREDCREDITSDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/DEBT" xlink:type="simple" xlink:href="aat-20200331.xsd#DEBT"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DEBT" xlink:type="extended" id="i0b109cbed6b84d969c21ae5d98ebe2a6_DEBT"/>
<link:roleRef roleURI="http://www.americanassets.com/role/DEBTTables" xlink:type="simple" xlink:href="aat-20200331.xsd#DEBTTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DEBTTables" xlink:type="extended" id="i38dc9cf1b5a5423796e995ac80e31649_DEBTTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/DEBTSummaryofTotalSecuredNotesPayableOutstandingDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#DEBTSummaryofTotalSecuredNotesPayableOutstandingDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DEBTSummaryofTotalSecuredNotesPayableOutstandingDetails" xlink:type="extended" id="i2c4c3ce446e6446ea724ebe6b5dba9fa_DEBTSummaryofTotalSecuredNotesPayableOutstandingDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_cfd16655-eeab-4b6a-b041-853d92342723" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_cfd16655-eeab-4b6a-b041-853d92342723" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_c9e1016b-3420-4269-be9a-629ccfda35af" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_c9e1016b-3420-4269-be9a-629ccfda35af" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_76d9431c-4e85-4d56-b3e6-5a79c843eba3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentMaturityDate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_76d9431c-4e85-4d56-b3e6-5a79c843eba3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_d9215a34-1758-46f5-8331-5fe5828ada3c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_d9215a34-1758-46f5-8331-5fe5828ada3c" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_f337fa01-103e-43cf-bc5d-1dd4bd734919" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_LongTermDebt_f337fa01-103e-43cf-bc5d-1dd4bd734919" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PeriodOfAmortizationSchedule_4671ba46-5e83-4a7f-927a-de81c2421bfc" xlink:href="aat-20200331.xsd#aat_PeriodOfAmortizationSchedule"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_aat_PeriodOfAmortizationSchedule_4671ba46-5e83-4a7f-927a-de81c2421bfc" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_af529bc3-7f4e-4b81-a8ca-3fef5031da87" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedAmortizationDeferredFinanceCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_af529bc3-7f4e-4b81-a8ca-3fef5031da87" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c8805e49-0c82-455a-ad68-5408b1a7f710" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7a21fd02-551a-4c84-842d-fcac1e4de9a0" xlink:to="loc_us-gaap_DebtInstrumentTable_c8805e49-0c82-455a-ad68-5408b1a7f710" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_9db335a6-cc51-4d42-9fd6-beba2481ec03" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c8805e49-0c82-455a-ad68-5408b1a7f710" xlink:to="loc_dei_LegalEntityAxis_9db335a6-cc51-4d42-9fd6-beba2481ec03" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_9db335a6-cc51-4d42-9fd6-beba2481ec03_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_9db335a6-cc51-4d42-9fd6-beba2481ec03" xlink:to="loc_dei_EntityDomain_9db335a6-cc51-4d42-9fd6-beba2481ec03_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_4ea0d974-afe8-47f3-8b37-91949d16a703" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_9db335a6-cc51-4d42-9fd6-beba2481ec03" xlink:to="loc_dei_EntityDomain_4ea0d974-afe8-47f3-8b37-91949d16a703" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_eaaed652-b94c-4915-8144-efd85c0cc12c" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_4ea0d974-afe8-47f3-8b37-91949d16a703" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_eaaed652-b94c-4915-8144-efd85c0cc12c" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_c27a723f-fd6f-4d99-81a8-b49a7de8afe3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c8805e49-0c82-455a-ad68-5408b1a7f710" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_c27a723f-fd6f-4d99-81a8-b49a7de8afe3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c27a723f-fd6f-4d99-81a8-b49a7de8afe3_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c27a723f-fd6f-4d99-81a8-b49a7de8afe3" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c27a723f-fd6f-4d99-81a8-b49a7de8afe3_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d29c0943-7b9b-433a-a403-5b908a7b7325" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c27a723f-fd6f-4d99-81a8-b49a7de8afe3" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d29c0943-7b9b-433a-a403-5b908a7b7325" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_6b7fae99-a3fb-42de-a35a-9f7980a947ca" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d29c0943-7b9b-433a-a403-5b908a7b7325" xlink:to="loc_us-gaap_SecuredDebtMember_6b7fae99-a3fb-42de-a35a-9f7980a947ca" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c8805e49-0c82-455a-ad68-5408b1a7f710" xlink:to="loc_us-gaap_DebtInstrumentAxis_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_21cc6ed9-a2c8-414e-acf0-9318bb7dc9b1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TorreyReserveMember_2196f6c1-7c8a-42a9-83d5-6c1c6cfaa644" xlink:href="aat-20200331.xsd#aat_TorreyReserveMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:to="loc_aat_TorreyReserveMember_2196f6c1-7c8a-42a9-83d5-6c1c6cfaa644" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SolanaBeachCorporateCentreOneToTwoMember_b54bdc27-9b11-4c3e-b95f-f3be04d0db78" xlink:href="aat-20200331.xsd#aat_SolanaBeachCorporateCentreOneToTwoMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:to="loc_aat_SolanaBeachCorporateCentreOneToTwoMember_b54bdc27-9b11-4c3e-b95f-f3be04d0db78" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SolanaBeachTowneCentreMember_efd4b011-7ed8-4400-93e9-94e0042526ac" xlink:href="aat-20200331.xsd#aat_SolanaBeachTowneCentreMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:to="loc_aat_SolanaBeachTowneCentreMember_efd4b011-7ed8-4400-93e9-94e0042526ac" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_CityCenterBellevueMember_9e980198-046d-4e86-a826-bad6d89ee645" xlink:href="aat-20200331.xsd#aat_CityCenterBellevueMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dfdc67e7-082b-434c-a38f-1189f0eeffe5" xlink:to="loc_aat_CityCenterBellevueMember_9e980198-046d-4e86-a826-bad6d89ee645" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/DEBTSummaryofTotalUnsecuredNotesPayableOutstandingDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#DEBTSummaryofTotalUnsecuredNotesPayableOutstandingDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DEBTSummaryofTotalUnsecuredNotesPayableOutstandingDetails" xlink:type="extended" id="i094996ee17a743099666357fa493f24f_DEBTSummaryofTotalUnsecuredNotesPayableOutstandingDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_aaf39dfd-4979-488d-99e2-2b21c8a3a2c6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_aaf39dfd-4979-488d-99e2-2b21c8a3a2c6" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_6e125fb4-06c5-4806-8158-83b34d4841cd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_6e125fb4-06c5-4806-8158-83b34d4841cd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_3511ae39-ecd7-4788-ba90-6a199e7347dc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebt"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_LongTermDebt_3511ae39-ecd7-4788-ba90-6a199e7347dc" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1114d187-504b-45ff-a93f-6a56a21367f7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1114d187-504b-45ff-a93f-6a56a21367f7" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_16d92ebe-c62b-4cf1-a2a4-6ad7e5fa1cb5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentMaturityDate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_16d92ebe-c62b-4cf1-a2a4-6ad7e5fa1cb5" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_aaadf63e-fff9-40af-994b-cdf7a553bd37" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedAmortizationDeferredFinanceCosts"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_AccumulatedAmortizationDeferredFinanceCosts_aaadf63e-fff9-40af-994b-cdf7a553bd37" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_298db3c8-5067-4965-b3ad-dc816b756a8e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFixedInterestRate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_298db3c8-5067-4965-b3ad-dc816b756a8e" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTermOfContract_d153ab36-cb17-4e20-9ff8-3a1f66deb222" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeTermOfContract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DerivativeTermOfContract_d153ab36-cb17-4e20-9ff8-3a1f66deb222" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainOnDerivative_16d5b271-ca66-4279-9c3b-6a19e48cd5a7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainOnDerivative"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DerivativeGainOnDerivative_16d5b271-ca66-4279-9c3b-6a19e48cd5a7" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLossOnDerivative_05996d3a-1bcb-47ca-956c-ac92b07585e1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLossOnDerivative"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DerivativeLossOnDerivative_05996d3a-1bcb-47ca-956c-ac92b07585e1" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_14a4c651-8e11-4a90-b29f-99e25bbbce40" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_14a4c651-8e11-4a90-b29f-99e25bbbce40" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8898a4bc-d4e7-4d36-ab14-d2016f181f5c" xlink:to="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:to="loc_dei_LegalEntityAxis_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2" xlink:to="loc_dei_EntityDomain_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_634c7dba-b77e-462e-9076-6076bcae8312" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_d12308b7-1ec9-4b6f-968d-2e9fd9cb6db2" xlink:to="loc_dei_EntityDomain_634c7dba-b77e-462e-9076-6076bcae8312" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_0d3e46a5-f992-4440-b4aa-61acc999a8ba" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_634c7dba-b77e-462e-9076-6076bcae8312" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_0d3e46a5-f992-4440-b4aa-61acc999a8ba" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:to="loc_us-gaap_DebtInstrumentAxis_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_17c09ba5-3ec3-4d82-80f3-aa900e3e7d85" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanAMember_1b3cd3e4-28a7-4060-88ed-852c27cf2590" xlink:href="aat-20200331.xsd#aat_TermLoanAMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_TermLoanAMember_1b3cd3e4-28a7-4060-88ed-852c27cf2590" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesAMember_26978413-2abe-4aeb-b942-d9656cbf5a1d" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesAMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesAMember_26978413-2abe-4aeb-b942-d9656cbf5a1d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanBMember_fbf77f2d-7e20-4583-8524-a3568ab036be" xlink:href="aat-20200331.xsd#aat_TermLoanBMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_TermLoanBMember_fbf77f2d-7e20-4583-8524-a3568ab036be" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanCMember_5290a7a4-6e37-4717-a078-8971ce90b890" xlink:href="aat-20200331.xsd#aat_TermLoanCMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_TermLoanCMember_5290a7a4-6e37-4717-a078-8971ce90b890" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesFMember_620deff6-250b-48b8-af83-c9a5a028c39c" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesFMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesFMember_620deff6-250b-48b8-af83-c9a5a028c39c" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesBMember_ab1d07dc-c2e8-434c-af97-0f0874d2da1c" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesBMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesBMember_ab1d07dc-c2e8-434c-af97-0f0874d2da1c" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesCMember_6aefe822-0196-4db1-a285-b2fd8a32029f" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesCMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesCMember_6aefe822-0196-4db1-a285-b2fd8a32029f" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesDMember_9b41fef2-2845-4345-a1dd-b86e42c98217" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesDMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesDMember_9b41fef2-2845-4345-a1dd-b86e42c98217" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesEMember_eae4616d-238f-4f50-befe-d5c0bd95f95f" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesEMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesEMember_eae4616d-238f-4f50-befe-d5c0bd95f95f" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesGMember_177a37ef-00bf-4446-bf8f-90531190af93" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesGMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_47aaae7b-9ed9-4eea-83bf-9763e4440f76" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesGMember_177a37ef-00bf-4446-bf8f-90531190af93" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_46f01257-4291-443f-945a-98565525c17f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_46f01257-4291-443f-945a-98565525c17f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_46f01257-4291-443f-945a-98565525c17f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_46f01257-4291-443f-945a-98565525c17f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_46f01257-4291-443f-945a-98565525c17f_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a7d363b3-b442-4cd1-848d-cd222c6f3727" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_46f01257-4291-443f-945a-98565525c17f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a7d363b3-b442-4cd1-848d-cd222c6f3727" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_9fbc2983-c83f-467d-8783-74c132b99a3a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnsecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a7d363b3-b442-4cd1-848d-cd222c6f3727" xlink:to="loc_us-gaap_UnsecuredDebtMember_9fbc2983-c83f-467d-8783-74c132b99a3a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_18f2a210-4d61-4530-9b4e-59052c3b9a34" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d1f344be-52b6-4a34-9bef-97dad42371b7" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_18f2a210-4d61-4530-9b4e-59052c3b9a34" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_18f2a210-4d61-4530-9b4e-59052c3b9a34_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_18f2a210-4d61-4530-9b4e-59052c3b9a34" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_18f2a210-4d61-4530-9b4e-59052c3b9a34_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4b89a2a3-52ff-4f55-bdb4-2944c4c1f9e0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_18f2a210-4d61-4530-9b4e-59052c3b9a34" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4b89a2a3-52ff-4f55-bdb4-2944c4c1f9e0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_ed64fc06-141d-43b4-8dca-62e4a4bda0b0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateSwapMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4b89a2a3-52ff-4f55-bdb4-2944c4c1f9e0" xlink:to="loc_us-gaap_InterestRateSwapMember_ed64fc06-141d-43b4-8dca-62e4a4bda0b0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_c6f42f7f-ecbe-438c-9c4d-e5e0ee110b9b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForwardContractsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4b89a2a3-52ff-4f55-bdb4-2944c4c1f9e0" xlink:to="loc_us-gaap_ForwardContractsMember_c6f42f7f-ecbe-438c-9c4d-e5e0ee110b9b" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/DEBTDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#DEBTDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/DEBTDetails" xlink:type="extended" id="i6376158164084fe4b7fd2763aaddad03_DEBTDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_e460f73f-bdbc-4c9b-9cbf-ebe9edff6248" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_e460f73f-bdbc-4c9b-9cbf-ebe9edff6248" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_5507206c-799b-40d6-8765-9658d20f7883" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentTerm_5507206c-799b-40d6-8765-9658d20f7883" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_c095e3cd-a240-416a-9e67-3f4ed2761492" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_c095e3cd-a240-416a-9e67-3f4ed2761492" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_d50691a8-7528-4caa-9aa5-f90920614bfd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentDescriptionOfVariableRateBasis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_d50691a8-7528-4caa-9aa5-f90920614bfd" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_b862a46c-894a-478c-ba8f-f9a2b82f9a8a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_b862a46c-894a-478c-ba8f-f9a2b82f9a8a" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentVariableRateBasisFour._9a5eb380-b1b8-4843-88a2-a25e423c7ecb" xlink:href="aat-20200331.xsd#aat_DebtInstrumentVariableRateBasisFour."/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentVariableRateBasisFour._9a5eb380-b1b8-4843-88a2-a25e423c7ecb" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentVariableRateBasisOne_f842c623-8312-403d-803d-8d442929fc4f" xlink:href="aat-20200331.xsd#aat_DebtInstrumentVariableRateBasisOne"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentVariableRateBasisOne_f842c623-8312-403d-803d-8d442929fc4f" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentVariableRateBasisTwo_1bb5e0f0-c8ab-45e7-bfa1-656c7a8cf134" xlink:href="aat-20200331.xsd#aat_DebtInstrumentVariableRateBasisTwo"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentVariableRateBasisTwo_1bb5e0f0-c8ab-45e7-bfa1-656c7a8cf134" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentSpreadonVariableRateBasisTwo_30a4d116-4c3a-45c5-81f1-fa936a56fe7b" xlink:href="aat-20200331.xsd#aat_DebtInstrumentSpreadonVariableRateBasisTwo"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentSpreadonVariableRateBasisTwo_30a4d116-4c3a-45c5-81f1-fa936a56fe7b" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentVariableRateBasisThree_683992dd-e865-4437-814f-92f06cd11a21" xlink:href="aat-20200331.xsd#aat_DebtInstrumentVariableRateBasisThree"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentVariableRateBasisThree_683992dd-e865-4437-814f-92f06cd11a21" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentSpreadonVariableRateBasisThree_e18c1092-3e7a-462a-b214-e6601ed75eee" xlink:href="aat-20200331.xsd#aat_DebtInstrumentSpreadonVariableRateBasisThree"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentSpreadonVariableRateBasisThree_e18c1092-3e7a-462a-b214-e6601ed75eee" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_f18577ab-0b0f-401c-89a7-c5af1e1569b3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_f18577ab-0b0f-401c-89a7-c5af1e1569b3" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LineofCreditFacilityAllowableAdditionalBorrowingCapacity_547b2db4-2b17-434e-b781-f81fabb899ba" xlink:href="aat-20200331.xsd#aat_LineofCreditFacilityAllowableAdditionalBorrowingCapacity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_LineofCreditFacilityAllowableAdditionalBorrowingCapacity_547b2db4-2b17-434e-b781-f81fabb899ba" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_22debdb7-9689-489e-9a7e-2e67078d05bb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_LineOfCredit_22debdb7-9689-489e-9a7e-2e67078d05bb" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet_67d88208-9ab1-409f-bbff-2d901acd56ab" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtIssuanceCostsLineOfCreditArrangementsNet_67d88208-9ab1-409f-bbff-2d901acd56ab" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentExtensionOptions_701b845c-2f75-4667-ad8e-e313ebb047a4" xlink:href="aat-20200331.xsd#aat_DebtInstrumentExtensionOptions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentExtensionOptions_701b845c-2f75-4667-ad8e-e313ebb047a4" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DebtInstrumentExtensionTerm_7ef75925-a8ad-4164-9ec5-d37548f0da1c" xlink:href="aat-20200331.xsd#aat_DebtInstrumentExtensionTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_DebtInstrumentExtensionTerm_7ef75925-a8ad-4164-9ec5-d37548f0da1c" xlink:type="arc" order="16"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MinimumFixedChargeCoverageRatioOnRevolvingCreditFacility_a50a08f6-52ff-4890-b3bf-b73764d104ef" xlink:href="aat-20200331.xsd#aat_MinimumFixedChargeCoverageRatioOnRevolvingCreditFacility"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_MinimumFixedChargeCoverageRatioOnRevolvingCreditFacility_a50a08f6-52ff-4890-b3bf-b73764d104ef" xlink:type="arc" order="17"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MinimumUnsecuredInterestCoverageRatio_45e1b753-a801-40e4-bbf4-5e344d347836" xlink:href="aat-20200331.xsd#aat_MinimumUnsecuredInterestCoverageRatio"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_MinimumUnsecuredInterestCoverageRatio_45e1b753-a801-40e4-bbf4-5e344d347836" xlink:type="arc" order="18"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LineOfCreditFacilityMaximumLeveragePercentage_5d7a3ff3-d364-4252-93fa-ffc755cbfa20" xlink:href="aat-20200331.xsd#aat_LineOfCreditFacilityMaximumLeveragePercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_LineOfCreditFacilityMaximumLeveragePercentage_5d7a3ff3-d364-4252-93fa-ffc755cbfa20" xlink:type="arc" order="19"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MaximumSecuredLeverageRatioOnRevolvingCreditFacility_2a97e578-808c-436e-bfc3-53d5600ffc66" xlink:href="aat-20200331.xsd#aat_MaximumSecuredLeverageRatioOnRevolvingCreditFacility"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_MaximumSecuredLeverageRatioOnRevolvingCreditFacility_2a97e578-808c-436e-bfc3-53d5600ffc66" xlink:type="arc" order="20"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MaximumUnsecuredLeverageRatio_0359dcf6-50dc-4a66-9cc1-d76235f69823" xlink:href="aat-20200331.xsd#aat_MaximumUnsecuredLeverageRatio"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_MaximumUnsecuredLeverageRatio_0359dcf6-50dc-4a66-9cc1-d76235f69823" xlink:type="arc" order="21"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MaximumRecourseIndebtednessofTotalAssetValue_e04a43a3-df8b-4cda-95bd-3a1f124d2b78" xlink:href="aat-20200331.xsd#aat_MaximumRecourseIndebtednessofTotalAssetValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_aat_MaximumRecourseIndebtednessofTotalAssetValue_e04a43a3-df8b-4cda-95bd-3a1f124d2b78" xlink:type="arc" order="22"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d255447f-5361-4aa0-9637-16878578f1cd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d255447f-5361-4aa0-9637-16878578f1cd" xlink:type="arc" order="23"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_38af4bc9-5b98-4e8a-8d9d-251a28aa2509" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentMaturityDate"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_38af4bc9-5b98-4e8a-8d9d-251a28aa2509" xlink:type="arc" order="24"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_8735e8bc-8424-4324-ada6-40ec160f8cc4" xlink:to="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_41c3c337-7604-41d9-8578-5a8ade243cb9" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_dei_LegalEntityAxis_41c3c337-7604-41d9-8578-5a8ade243cb9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_41c3c337-7604-41d9-8578-5a8ade243cb9_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_41c3c337-7604-41d9-8578-5a8ade243cb9" xlink:to="loc_dei_EntityDomain_41c3c337-7604-41d9-8578-5a8ade243cb9_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_11de0811-fbdb-489d-98c7-13b4b38c4553" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_41c3c337-7604-41d9-8578-5a8ade243cb9" xlink:to="loc_dei_EntityDomain_11de0811-fbdb-489d-98c7-13b4b38c4553" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_78ccedc3-d553-42c4-9f57-bff086d0a37a" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_11de0811-fbdb-489d-98c7-13b4b38c4553" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_78ccedc3-d553-42c4-9f57-bff086d0a37a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fe9e873d-6e51-4b8f-9799-ddc6d4c004f3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d8ff1a69-0d1f-42b7-8f9d-c77dcefc3e5d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fe9e873d-6e51-4b8f-9799-ddc6d4c004f3" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_b4ecedbc-9eb8-48f0-944b-7f86ba5212a9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnsecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fe9e873d-6e51-4b8f-9799-ddc6d4c004f3" xlink:to="loc_us-gaap_UnsecuredDebtMember_b4ecedbc-9eb8-48f0-944b-7f86ba5212a9" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_29b51490-6464-49fa-b43e-1897c75eef42" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fe9e873d-6e51-4b8f-9799-ddc6d4c004f3" xlink:to="loc_us-gaap_LineOfCreditMember_29b51490-6464-49fa-b43e-1897c75eef42" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e2543471-97a4-4c89-8721-919c037ee63c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_us-gaap_DebtInstrumentAxis_e2543471-97a4-4c89-8721-919c037ee63c" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e2543471-97a4-4c89-8721-919c037ee63c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e2543471-97a4-4c89-8721-919c037ee63c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e2543471-97a4-4c89-8721-919c037ee63c_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e2543471-97a4-4c89-8721-919c037ee63c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SeniorGuaranteedNotesSeriesGMember_b921e169-556f-4007-af4e-eacbeb2f5915" xlink:href="aat-20200331.xsd#aat_SeniorGuaranteedNotesSeriesGMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_SeniorGuaranteedNotesSeriesGMember_b921e169-556f-4007-af4e-eacbeb2f5915" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanBMember_a8d6cb37-8456-46e1-9f6f-a5bb1d898f41" xlink:href="aat-20200331.xsd#aat_TermLoanBMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_TermLoanBMember_a8d6cb37-8456-46e1-9f6f-a5bb1d898f41" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanCMember_dd3857a0-0440-4ad8-9153-06bf7a348d24" xlink:href="aat-20200331.xsd#aat_TermLoanCMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_TermLoanCMember_dd3857a0-0440-4ad8-9153-06bf7a348d24" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanAMember_785c369d-df8f-43e5-abbc-3ed6ba6c33fc" xlink:href="aat-20200331.xsd#aat_TermLoanAMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_TermLoanAMember_785c369d-df8f-43e5-abbc-3ed6ba6c33fc" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TermLoanBTermLoanCMember_fabeb008-2dc4-493e-89e8-da2febc47b04" xlink:href="aat-20200331.xsd#aat_TermLoanBTermLoanCMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_TermLoanBTermLoanCMember_fabeb008-2dc4-493e-89e8-da2febc47b04" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SecondAmendedandRestatedCreditFacilityMember_8a0addc5-18cc-408d-8613-064bb2c10fb4" xlink:href="aat-20200331.xsd#aat_SecondAmendedandRestatedCreditFacilityMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_31b0e18d-cf25-40ad-adca-9bcfe8945760" xlink:to="loc_aat_SecondAmendedandRestatedCreditFacilityMember_8a0addc5-18cc-408d-8613-064bb2c10fb4" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_840d471c-a9db-4487-8834-f1c9d320da36" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_840d471c-a9db-4487-8834-f1c9d320da36" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_840d471c-a9db-4487-8834-f1c9d320da36_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_840d471c-a9db-4487-8834-f1c9d320da36" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_840d471c-a9db-4487-8834-f1c9d320da36_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_923312f9-cb1e-4986-98ff-4a8884f2e2ab" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_840d471c-a9db-4487-8834-f1c9d320da36" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_923312f9-cb1e-4986-98ff-4a8884f2e2ab" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_0cfff5e4-d72b-42a5-b412-1dcfd56cdd25" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateSwapMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_923312f9-cb1e-4986-98ff-4a8884f2e2ab" xlink:to="loc_us-gaap_InterestRateSwapMember_0cfff5e4-d72b-42a5-b412-1dcfd56cdd25" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_3ee2d546-5201-451a-9598-5043ace13942" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_srt_RangeAxis_3ee2d546-5201-451a-9598-5043ace13942" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3ee2d546-5201-451a-9598-5043ace13942_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_3ee2d546-5201-451a-9598-5043ace13942" xlink:to="loc_srt_RangeMember_3ee2d546-5201-451a-9598-5043ace13942_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d1113473-088e-4acf-ab62-30e859e17411" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_3ee2d546-5201-451a-9598-5043ace13942" xlink:to="loc_srt_RangeMember_d1113473-088e-4acf-ab62-30e859e17411" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_98018522-01ba-4cd9-8816-f7723a6e5467" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d1113473-088e-4acf-ab62-30e859e17411" xlink:to="loc_srt_MinimumMember_98018522-01ba-4cd9-8816-f7723a6e5467" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_5f1832e7-d3f9-4a5c-bdd7-75b8c91c6ad0" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_d1113473-088e-4acf-ab62-30e859e17411" xlink:to="loc_srt_MaximumMember_5f1832e7-d3f9-4a5c-bdd7-75b8c91c6ad0" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_006eb0a6-9db4-471f-a036-a93ea7408996" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_us-gaap_VariableRateAxis_006eb0a6-9db4-471f-a036-a93ea7408996" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_006eb0a6-9db4-471f-a036-a93ea7408996_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_006eb0a6-9db4-471f-a036-a93ea7408996" xlink:to="loc_us-gaap_VariableRateDomain_006eb0a6-9db4-471f-a036-a93ea7408996_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_006eb0a6-9db4-471f-a036-a93ea7408996" xlink:to="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_cccc85d2-28ae-478a-9c15-53a4df595ec7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_cccc85d2-28ae-478a-9c15-53a4df595ec7" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_f5e3a5f6-fd93-4188-ad2e-1a2143e8f24c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BaseRateMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:to="loc_us-gaap_BaseRateMember_f5e3a5f6-fd93-4188-ad2e-1a2143e8f24c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FederalFundsRateMember_27c2ab95-6442-4920-990c-b7afcd7bd98f" xlink:href="aat-20200331.xsd#aat_FederalFundsRateMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:to="loc_aat_FederalFundsRateMember_27c2ab95-6442-4920-990c-b7afcd7bd98f" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EurodollarMember_039bead2-f339-4411-8fdd-dfa987fc2b01" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EurodollarMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_e000db19-5026-4fa2-8f05-536fae5fdcdd" xlink:to="loc_us-gaap_EurodollarMember_039bead2-f339-4411-8fdd-dfa987fc2b01" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_f616bbb3-6bf5-429c-b012-c42c52462842" xlink:to="loc_us-gaap_CreditFacilityAxis_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b" xlink:to="loc_us-gaap_CreditFacilityDomain_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_b746fc89-1b5a-45fa-9ab2-7d55c1425733" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_5f8a5ad2-6a74-4c3c-a477-73d1b070ee1b" xlink:to="loc_us-gaap_CreditFacilityDomain_b746fc89-1b5a-45fa-9ab2-7d55c1425733" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_b28c59ee-914a-415f-b695-285fd13e0e90" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_b746fc89-1b5a-45fa-9ab2-7d55c1425733" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_b28c59ee-914a-415f-b695-285fd13e0e90" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/PARTNERSCAPITALOFAMERICANASSETSTRUSTLP" xlink:type="simple" xlink:href="aat-20200331.xsd#PARTNERSCAPITALOFAMERICANASSETSTRUSTLP"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/PARTNERSCAPITALOFAMERICANASSETSTRUSTLP" xlink:type="extended" id="ib171323eca9143b299aa8df2d28bb41e_PARTNERSCAPITALOFAMERICANASSETSTRUSTLP"/>
<link:roleRef roleURI="http://www.americanassets.com/role/PARTNERSCAPITALOFAMERICANASSETSTRUSTLPDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#PARTNERSCAPITALOFAMERICANASSETSTRUSTLPDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/PARTNERSCAPITALOFAMERICANASSETSTRUSTLPDetails" xlink:type="extended" id="i0d8620de1fa24073a8fb4b56dad7c3a7_PARTNERSCAPITALOFAMERICANASSETSTRUSTLPDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CapitalUnitLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SharesHeldByMinorityInterestInOperatingPartnerships_781ba8b2-f2fe-4cc2-98d4-c85f3bdc3a11" xlink:href="aat-20200331.xsd#aat_SharesHeldByMinorityInterestInOperatingPartnerships"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_aat_SharesHeldByMinorityInterestInOperatingPartnerships_781ba8b2-f2fe-4cc2-98d4-c85f3bdc3a11" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_243d5e80-1bf3-44ea-979f-5e66a44c6c7a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_243d5e80-1bf3-44ea-979f-5e66a44c6c7a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PartnersCapitalRedemptionConversionRatio_0ce36367-956f-48f0-a2a9-3200e2ce88cc" xlink:href="aat-20200331.xsd#aat_PartnersCapitalRedemptionConversionRatio"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_aat_PartnersCapitalRedemptionConversionRatio_0ce36367-956f-48f0-a2a9-3200e2ce88cc" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_41a8dd28-f13f-482b-8e24-19e428b78009" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_41a8dd28-f13f-482b-8e24-19e428b78009" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding_7dadcba7-e248-44ab-b650-5713c454c181" xlink:href="aat-20200331.xsd#aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding_7dadcba7-e248-44ab-b650-5713c454c181" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_78af9146-d250-4976-b1c8-c547f562d37e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_78af9146-d250-4976-b1c8-c547f562d37e" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfCapitalUnitsTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalUnitLineItems_f03d8c9a-4dff-4575-8bb2-1752c374a3d0" xlink:to="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_238b5ddc-a527-42e1-8aa5-e4579105a0c9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_238b5ddc-a527-42e1-8aa5-e4579105a0c9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_238b5ddc-a527-42e1-8aa5-e4579105a0c9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_238b5ddc-a527-42e1-8aa5-e4579105a0c9" xlink:to="loc_us-gaap_EquityComponentDomain_238b5ddc-a527-42e1-8aa5-e4579105a0c9_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6d38b7b5-de8d-4ae9-a3aa-133a056f8b24" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_238b5ddc-a527-42e1-8aa5-e4579105a0c9" xlink:to="loc_us-gaap_EquityComponentDomain_6d38b7b5-de8d-4ae9-a3aa-133a056f8b24" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9f76211d-b6f6-45b8-a64c-64dc203fa115" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6d38b7b5-de8d-4ae9-a3aa-133a056f8b24" xlink:to="loc_us-gaap_CommonStockMember_9f76211d-b6f6-45b8-a64c-64dc203fa115" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e158d307-8731-4f58-a9ee-206d99159ac5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e158d307-8731-4f58-a9ee-206d99159ac5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_e158d307-8731-4f58-a9ee-206d99159ac5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e158d307-8731-4f58-a9ee-206d99159ac5" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_e158d307-8731-4f58-a9ee-206d99159ac5_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_915c00c6-6208-458e-982b-217b904d4468" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_e158d307-8731-4f58-a9ee-206d99159ac5" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_915c00c6-6208-458e-982b-217b904d4468" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_99748afe-d4c5-46b6-9983-0ca504be6109" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LimitedPartnerMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_915c00c6-6208-458e-982b-217b904d4468" xlink:to="loc_us-gaap_LimitedPartnerMember_99748afe-d4c5-46b6-9983-0ca504be6109" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:to="loc_dei_LegalEntityAxis_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a" xlink:to="loc_dei_EntityDomain_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3e0b1758-61fb-4d3e-b598-d2772c362889" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_3c8a51d1-d7ea-4ce3-89b4-373078cf0c9a" xlink:to="loc_dei_EntityDomain_3e0b1758-61fb-4d3e-b598-d2772c362889" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_2c5f7ffb-405d-495c-b868-7d96d69c74d0" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3e0b1758-61fb-4d3e-b598-d2772c362889" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_2c5f7ffb-405d-495c-b868-7d96d69c74d0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3e6c9d5e-c7f4-419c-bafc-68a1733b0954" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3e6c9d5e-c7f4-419c-bafc-68a1733b0954" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3e6c9d5e-c7f4-419c-bafc-68a1733b0954_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3e6c9d5e-c7f4-419c-bafc-68a1733b0954" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_3e6c9d5e-c7f4-419c-bafc-68a1733b0954_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80d3b4a1-0d78-455c-a4ae-e25aa3c4923d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3e6c9d5e-c7f4-419c-bafc-68a1733b0954" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80d3b4a1-0d78-455c-a4ae-e25aa3c4923d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OperatingPartnershipUnitsMember_509892dd-7f6f-400a-b832-546d3367b64d" xlink:href="aat-20200331.xsd#aat_OperatingPartnershipUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80d3b4a1-0d78-455c-a4ae-e25aa3c4923d" xlink:to="loc_aat_OperatingPartnershipUnitsMember_509892dd-7f6f-400a-b832-546d3367b64d" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_OwnershipAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCapitalUnitsTable_b9336776-c245-487d-ba1a-a0e96eace4b1" xlink:to="loc_srt_OwnershipAxis_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_OwnershipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab" xlink:to="loc_srt_OwnershipDomain_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_664dfe43-3864-4c0c-adc5-b7f06f4162ce" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_OwnershipDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_e4a6e148-c910-4b4e-b67a-8dbefd2bb0ab" xlink:to="loc_srt_OwnershipDomain_664dfe43-3864-4c0c-adc5-b7f06f4162ce" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_e7d68821-ebb5-4cdf-a2a6-5962d588b259" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_664dfe43-3864-4c0c-adc5-b7f06f4162ce" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_e7d68821-ebb5-4cdf-a2a6-5962d588b259" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINC" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINC"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINC" xlink:type="extended" id="i7375e0780cd2473ea6d8843e0bf4d870_EQUITYOFAMERICANASSETSTRUSTINC"/>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCTables" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCTables" xlink:type="extended" id="i33cdc8a5c88c45b592d12ff790a33bdb_EQUITYOFAMERICANASSETSTRUSTINCTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCDetails" xlink:type="extended" id="i86aa15446c4741d08902d5827baa66c5_EQUITYOFAMERICANASSETSTRUSTINCDetails">
<link:loc xlink:type="locator" xlink:label="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:href="aat-20200331.xsd#aat_EquityLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_NumberofSalesAgents_8f439cb2-7727-494f-83bc-2feced0367d1" xlink:href="aat-20200331.xsd#aat_NumberofSalesAgents"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_aat_NumberofSalesAgents_8f439cb2-7727-494f-83bc-2feced0367d1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AggregateOfferingPriceOfCommonShare_643c54f3-3b98-4370-b232-87bebfd92d3f" xlink:href="aat-20200331.xsd#aat_AggregateOfferingPriceOfCommonShare"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_aat_AggregateOfferingPriceOfCommonShare_643c54f3-3b98-4370-b232-87bebfd92d3f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_ef1dd893-8c0e-4060-a337-a9a027668cb6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_ef1dd893-8c0e-4060-a337-a9a027668cb6" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_79059a4d-134e-418e-a3dc-a26ef9d70118" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_79059a4d-134e-418e-a3dc-a26ef9d70118" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RemainingCapacityToIssue_694365e2-d59e-451d-83b1-2eee56be9052" xlink:href="aat-20200331.xsd#aat_RemainingCapacityToIssue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_aat_RemainingCapacityToIssue_694365e2-d59e-451d-83b1-2eee56be9052" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_07f845ac-6118-4f60-944a-1c9a2b928643" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_CommonStockSharesIssued_07f845ac-6118-4f60-944a-1c9a2b928643" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_9f265613-32c6-4d17-b079-a69d305eb4bc" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_RestrictedStockExpense_9f265613-32c6-4d17-b079-a69d305eb4bc" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_2c3d1cb0-0860-4dc4-a6af-eee994d0bdf8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_2c3d1cb0-0860-4dc4-a6af-eee994d0bdf8" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding_fecf4234-adb6-40a8-b8b1-09092fb22571" xlink:href="aat-20200331.xsd#aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_aat_WeightedAverageUnvestedParticipatingSecuritiesOutstanding_fecf4234-adb6-40a8-b8b1-09092fb22571" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_05bcbdd2-0e40-4c89-9924-bf4a2f871a0f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_05bcbdd2-0e40-4c89-9924-bf4a2f871a0f" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:href="aat-20200331.xsd#aat_EquityTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_aat_EquityLineItems_c21e2ca5-0e50-4185-adda-dbef757b33c2" xlink:to="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_9d58500f-2d07-49e4-93a4-4a33b3d40c04" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:to="loc_dei_LegalEntityAxis_9d58500f-2d07-49e4-93a4-4a33b3d40c04" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_9d58500f-2d07-49e4-93a4-4a33b3d40c04_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_9d58500f-2d07-49e4-93a4-4a33b3d40c04" xlink:to="loc_dei_EntityDomain_9d58500f-2d07-49e4-93a4-4a33b3d40c04_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_aeaa8765-fa69-4379-b2cb-7b9a7ae3574e" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_9d58500f-2d07-49e4-93a4-4a33b3d40c04" xlink:to="loc_dei_EntityDomain_aeaa8765-fa69-4379-b2cb-7b9a7ae3574e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_93e41e9a-d1fc-4870-857c-ab3c56d68ac0" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_aeaa8765-fa69-4379-b2cb-7b9a7ae3574e" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_93e41e9a-d1fc-4870-857c-ab3c56d68ac0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0a98dcde-1882-4e8c-a520-942cc2d21e89" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_e8b389ae-d2ff-4814-8b1b-9b37ccd37efb" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0a98dcde-1882-4e8c-a520-942cc2d21e89" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OperatingPartnershipUnitsMember_7b273a9e-9d29-4180-b8f7-8434393be207" xlink:href="aat-20200331.xsd#aat_OperatingPartnershipUnitsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_0a98dcde-1882-4e8c-a520-942cc2d21e89" xlink:to="loc_aat_OperatingPartnershipUnitsMember_7b273a9e-9d29-4180-b8f7-8434393be207" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_c627fc38-109d-4d78-9e09-ea43766e6e0f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_c627fc38-109d-4d78-9e09-ea43766e6e0f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_c627fc38-109d-4d78-9e09-ea43766e6e0f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_c627fc38-109d-4d78-9e09-ea43766e6e0f" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_c627fc38-109d-4d78-9e09-ea43766e6e0f_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7fac3ea9-e044-409e-8f35-73bb7f6dd48d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_c627fc38-109d-4d78-9e09-ea43766e6e0f" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7fac3ea9-e044-409e-8f35-73bb7f6dd48d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AtMarketEquityProgramMember_ef0dd25c-df96-4ddf-b6f7-949de83b69e5" xlink:href="aat-20200331.xsd#aat_AtMarketEquityProgramMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_7fac3ea9-e044-409e-8f35-73bb7f6dd48d" xlink:to="loc_aat_AtMarketEquityProgramMember_ef0dd25c-df96-4ddf-b6f7-949de83b69e5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_3d69f7cd-dcf8-439a-b8c5-504637416d79" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_EquityTable_7346d7a8-4976-43e1-a726-0bb34c53bf54" xlink:to="loc_us-gaap_AwardTypeAxis_3d69f7cd-dcf8-439a-b8c5-504637416d79" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3d69f7cd-dcf8-439a-b8c5-504637416d79_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_3d69f7cd-dcf8-439a-b8c5-504637416d79" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3d69f7cd-dcf8-439a-b8c5-504637416d79_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b9b80c28-7aa1-4f33-809d-d08e534fca77" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_3d69f7cd-dcf8-439a-b8c5-504637416d79" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b9b80c28-7aa1-4f33-809d-d08e534fca77" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_cbf2c6c4-2e7d-4ac5-b943-5a74c5600d83" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_b9b80c28-7aa1-4f33-809d-d08e534fca77" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_cbf2c6c4-2e7d-4ac5-b943-5a74c5600d83" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCATMEquityProgramDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCATMEquityProgramDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCATMEquityProgramDetails" xlink:type="extended" id="if48efcc8c5ec475eabbc7e8b12408356_EQUITYOFAMERICANASSETSTRUSTINCATMEquityProgramDetails">
<link:loc xlink:type="locator" xlink:label="loc_aat_EquityLineItems_27767b2a-82f9-48a2-a307-91b5ee82f92a" xlink:href="aat-20200331.xsd#aat_EquityLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_991a838c-31a0-4822-91e6-86677bff2c97" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_27767b2a-82f9-48a2-a307-91b5ee82f92a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_991a838c-31a0-4822-91e6-86677bff2c97" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_21ed289d-bae9-462b-9203-81b43b6d9d5b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_EquityLineItems_27767b2a-82f9-48a2-a307-91b5ee82f92a" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_21ed289d-bae9-462b-9203-81b43b6d9d5b" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_EquityTable_933d7896-6729-4161-9b58-12b82c6d5f62" xlink:href="aat-20200331.xsd#aat_EquityTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_aat_EquityLineItems_27767b2a-82f9-48a2-a307-91b5ee82f92a" xlink:to="loc_aat_EquityTable_933d7896-6729-4161-9b58-12b82c6d5f62" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_eee320f5-90b1-439d-bbbe-38773ba0d6ae" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_EquityTable_933d7896-6729-4161-9b58-12b82c6d5f62" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_eee320f5-90b1-439d-bbbe-38773ba0d6ae" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_eee320f5-90b1-439d-bbbe-38773ba0d6ae_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_eee320f5-90b1-439d-bbbe-38773ba0d6ae" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_eee320f5-90b1-439d-bbbe-38773ba0d6ae_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e6fcb39e-c541-45d9-b4e2-b6c681121901" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_eee320f5-90b1-439d-bbbe-38773ba0d6ae" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e6fcb39e-c541-45d9-b4e2-b6c681121901" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AtMarketEquityProgramMember_8632927e-58fd-446a-8dfc-0ae22380e920" xlink:href="aat-20200331.xsd#aat_AtMarketEquityProgramMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e6fcb39e-c541-45d9-b4e2-b6c681121901" xlink:to="loc_aat_AtMarketEquityProgramMember_8632927e-58fd-446a-8dfc-0ae22380e920" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCDividendsDeclareandPaidonSharesonCommonStockandNoncontrollingCommonUnitsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCDividendsDeclareandPaidonSharesonCommonStockandNoncontrollingCommonUnitsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCDividendsDeclareandPaidonSharesonCommonStockandNoncontrollingCommonUnitsDetails" xlink:type="extended" id="ie412737a09794bde80ae4f3ab509ae2d_EQUITYOFAMERICANASSETSTRUSTINCDividendsDeclareandPaidonSharesonCommonStockandNoncontrollingCommonUnitsDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCSummaryofActivityofRestrictedStockAwardsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCSummaryofActivityofRestrictedStockAwardsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCSummaryofActivityofRestrictedStockAwardsDetails" xlink:type="extended" id="i697eddfb02d04b2881ca6245fd37512d_EQUITYOFAMERICANASSETSTRUSTINCSummaryofActivityofRestrictedStockAwardsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_60076d07-e130-4064-bd68-0c2994c95bd6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_60076d07-e130-4064-bd68-0c2994c95bd6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_eccf32e5-f5d3-4c66-9ff2-32f37dab6f47" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_eccf32e5-f5d3-4c66-9ff2-32f37dab6f47" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_86afbd3c-b1a8-46e2-9134-3d3d9e5cfd44" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_86afbd3c-b1a8-46e2-9134-3d3d9e5cfd44" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_c670d9e6-8161-48df-95e9-b7ba8a00e3a2" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_c670d9e6-8161-48df-95e9-b7ba8a00e3a2" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_e1778105-93a8-4f80-88c8-bcb7fd1550b7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d6d0d96c-518e-4599-9ccd-0db7f7802415" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_e1778105-93a8-4f80-88c8-bcb7fd1550b7" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_879284fc-ed29-4211-9685-f321afe17265" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_60076d07-e130-4064-bd68-0c2994c95bd6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_28379370-05a9-4c1c-a282-84932b28111f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_28379370-05a9-4c1c-a282-84932b28111f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_eb1ffc35-b1cb-4e74-b38d-8b3dbd38b7d5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_eb1ffc35-b1cb-4e74-b38d-8b3dbd38b7d5" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_65a20334-fc72-4f34-8561-198baf0f178f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_65a20334-fc72-4f34-8561-198baf0f178f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_8363df18-8fbc-4dbe-932a-cd5094446cac" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_502c3698-f532-4001-97ea-26e631ee9339" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_8363df18-8fbc-4dbe-932a-cd5094446cac" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_f604fb90-ebaa-4ffb-b319-91017d92a01b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_5529f136-1b3b-479b-8a1e-1152be559b21" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockExpense"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_60076d07-e130-4064-bd68-0c2994c95bd6" xlink:to="loc_us-gaap_RestrictedStockExpense_5529f136-1b3b-479b-8a1e-1152be559b21" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8020f8a3-4d36-40b2-8c91-12bce2f035d8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_60076d07-e130-4064-bd68-0c2994c95bd6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8020f8a3-4d36-40b2-8c91-12bce2f035d8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_4f28db50-eac6-4d6d-a25a-66c275d3eb60" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_8020f8a3-4d36-40b2-8c91-12bce2f035d8" xlink:to="loc_us-gaap_AwardTypeAxis_4f28db50-eac6-4d6d-a25a-66c275d3eb60" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4f28db50-eac6-4d6d-a25a-66c275d3eb60_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_4f28db50-eac6-4d6d-a25a-66c275d3eb60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4f28db50-eac6-4d6d-a25a-66c275d3eb60_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_204b07c5-6b85-477a-bc95-332451069e1c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_4f28db50-eac6-4d6d-a25a-66c275d3eb60" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_204b07c5-6b85-477a-bc95-332451069e1c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_cddd3ad9-8eda-449e-91a6-0fcb775dc53d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_204b07c5-6b85-477a-bc95-332451069e1c" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_cddd3ad9-8eda-449e-91a6-0fcb775dc53d" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCComputationofBasicandDilutedEPSDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#EQUITYOFAMERICANASSETSTRUSTINCComputationofBasicandDilutedEPSDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/EQUITYOFAMERICANASSETSTRUSTINCComputationofBasicandDilutedEPSDetails" xlink:type="extended" id="i5154e37ede4b4b5b801599ff86be038c_EQUITYOFAMERICANASSETSTRUSTINCComputationofBasicandDilutedEPSDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/INCOMETAXES" xlink:type="simple" xlink:href="aat-20200331.xsd#INCOMETAXES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/INCOMETAXES" xlink:type="extended" id="i548838c43bf3489cad59df8a18b9763d_INCOMETAXES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/INCOMETAXESDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#INCOMETAXESDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/INCOMETAXESDetails" xlink:type="extended" id="ic01440c7ec954868b0d395dcb7bf66a9_INCOMETAXESDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMMITMENTSANDCONTINGENCIES" xlink:type="simple" xlink:href="aat-20200331.xsd#COMMITMENTSANDCONTINGENCIES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMMITMENTSANDCONTINGENCIES" xlink:type="extended" id="ib71a84ae9a64468c98b8d14604a5dde5_COMMITMENTSANDCONTINGENCIES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#COMMITMENTSANDCONTINGENCIESDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMMITMENTSANDCONTINGENCIESDetails" xlink:type="extended" id="i02b5734ad8ec466eb431284ab78925c9_COMMITMENTSANDCONTINGENCIESDetails">
<link:loc xlink:type="locator" xlink:label="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:href="aat-20200331.xsd#aat_CommitmentAndContingenciesLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyManagementFeePercentFee_31bf8c05-32da-466c-a342-b72123c0e18a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyManagementFeePercentFee"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_us-gaap_PropertyManagementFeePercentFee_31bf8c05-32da-466c-a342-b72123c0e18a" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_CalendarMonths_582531e3-c92d-4afd-86af-c46aa95d83ba" xlink:href="aat-20200331.xsd#aat_CalendarMonths"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_CalendarMonths_582531e3-c92d-4afd-86af-c46aa95d83ba" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MaximumPercentageOfHotelsFiscalYearGrossRevenuesPaidForAggregateYearlyManagementFee_22ff0b0d-0c02-4a2d-bc4b-76231c1e82dd" xlink:href="aat-20200331.xsd#aat_MaximumPercentageOfHotelsFiscalYearGrossRevenuesPaidForAggregateYearlyManagementFee"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_MaximumPercentageOfHotelsFiscalYearGrossRevenuesPaidForAggregateYearlyManagementFee_22ff0b0d-0c02-4a2d-bc4b-76231c1e82dd" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PreviousMonthsOfManagementFees_2da29b28-bcd9-4ce5-b1fa-dd551c47a4bb" xlink:href="aat-20200331.xsd#aat_PreviousMonthsOfManagementFees"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_PreviousMonthsOfManagementFees_2da29b28-bcd9-4ce5-b1fa-dd551c47a4bb" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFirstElevenYearsOfTerm_9af0533f-8e70-47f8-8c79-0e4ebf2db9d7" xlink:href="aat-20200331.xsd#aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFirstElevenYearsOfTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFirstElevenYearsOfTerm_9af0533f-8e70-47f8-8c79-0e4ebf2db9d7" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsInHotelManagementAgreementTerm_400d5a76-015a-428c-978a-79639450cc9a" xlink:href="aat-20200331.xsd#aat_YearsInHotelManagementAgreementTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_YearsInHotelManagementAgreementTerm_400d5a76-015a-428c-978a-79639450cc9a" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInTwelfthYearOfTerm_10a9ce84-a869-4bfa-854a-30384620267c" xlink:href="aat-20200331.xsd#aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInTwelfthYearOfTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInTwelfthYearOfTerm_10a9ce84-a869-4bfa-854a-30384620267c" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInThirteenthYearOfTerm_75cef726-5acb-4cfc-8df0-19fc132c84ac" xlink:href="aat-20200331.xsd#aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInThirteenthYearOfTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInThirteenthYearOfTerm_75cef726-5acb-4cfc-8df0-19fc132c84ac" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFourteenthYearOfTerm_56351481-3deb-40b4-942d-6e8ed0f33192" xlink:href="aat-20200331.xsd#aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFourteenthYearOfTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_HotelManagementAgreementDefaultPenaltyFactOrOfPreviousTwelveMonthsOfManagementFeesInFourteenthYearOfTerm_56351481-3deb-40b4-942d-6e8ed0f33192" xlink:type="arc" order="8"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_HotelManagementAgreementDefaultPenaltyFactorOfPreviousTwelveMonthsOfManagementFeesInFifteenthYearOfTerm_c7660528-4367-4dee-8c90-fe08899f27db" xlink:href="aat-20200331.xsd#aat_HotelManagementAgreementDefaultPenaltyFactorOfPreviousTwelveMonthsOfManagementFeesInFifteenthYearOfTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_HotelManagementAgreementDefaultPenaltyFactorOfPreviousTwelveMonthsOfManagementFeesInFifteenthYearOfTerm_c7660528-4367-4dee-8c90-fe08899f27db" xlink:type="arc" order="9"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsOfContract_2e6fcdc6-ed5f-4e81-9ead-699b59de986d" xlink:href="aat-20200331.xsd#aat_YearsOfContract"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_YearsOfContract_2e6fcdc6-ed5f-4e81-9ead-699b59de986d" xlink:type="arc" order="10"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PercentageOfHotelOccupancyGrossRevenuePaidForFranchiseRoyaltyFee_34090d98-3e52-445c-8d1c-b8a1d9e64248" xlink:href="aat-20200331.xsd#aat_PercentageOfHotelOccupancyGrossRevenuePaidForFranchiseRoyaltyFee"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_PercentageOfHotelOccupancyGrossRevenuePaidForFranchiseRoyaltyFee_34090d98-3e52-445c-8d1c-b8a1d9e64248" xlink:type="arc" order="11"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PercentageOfHotelOccupancyGrossRevenuePaidForProgramFee_20d919f3-1a54-4b6c-89fb-868a9a685bd5" xlink:href="aat-20200331.xsd#aat_PercentageOfHotelOccupancyGrossRevenuePaidForProgramFee"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_PercentageOfHotelOccupancyGrossRevenuePaidForProgramFee_20d919f3-1a54-4b6c-89fb-868a9a685bd5" xlink:type="arc" order="12"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossOnContractTerminationForDefault_bb6f34db-5165-4436-b208-7af677da3f64" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossOnContractTerminationForDefault"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_us-gaap_LossOnContractTerminationForDefault_bb6f34db-5165-4436-b208-7af677da3f64" xlink:type="arc" order="13"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsEnvironmentalRemediationLength_de925cd4-a234-4d02-8e71-0e62719f49af" xlink:href="aat-20200331.xsd#aat_YearsEnvironmentalRemediationLength"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_YearsEnvironmentalRemediationLength_de925cd4-a234-4d02-8e71-0e62719f49af" xlink:type="arc" order="14"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_NumberOfConsolidatedProperties_5858d38a-6354-43fc-9ef7-cc9585a53184" xlink:href="aat-20200331.xsd#aat_NumberOfConsolidatedProperties"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_NumberOfConsolidatedProperties_5858d38a-6354-43fc-9ef7-cc9585a53184" xlink:type="arc" order="15"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_59505966-692f-457f-866b-9f581e42d5ce" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_59505966-692f-457f-866b-9f581e42d5ce" xlink:type="arc" order="16"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MaximumPercentageOfRevenueProvidedByAnySingleTenant_3048dada-f7db-41d3-ae9a-5b3c630c9e60" xlink:href="aat-20200331.xsd#aat_MaximumPercentageOfRevenueProvidedByAnySingleTenant"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_MaximumPercentageOfRevenueProvidedByAnySingleTenant_3048dada-f7db-41d3-ae9a-5b3c630c9e60" xlink:type="arc" order="17"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:href="aat-20200331.xsd#aat_CommitmentAndContingenciesTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_aat_CommitmentAndContingenciesLineItems_95d434a1-fae8-4f73-b95a-271a16c81dac" xlink:to="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_64d4108c-0f5e-49c9-ad9c-ef60a228ef53" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_64d4108c-0f5e-49c9-ad9c-ef60a228ef53" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_64d4108c-0f5e-49c9-ad9c-ef60a228ef53_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_64d4108c-0f5e-49c9-ad9c-ef60a228ef53" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_64d4108c-0f5e-49c9-ad9c-ef60a228ef53_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_64d4108c-0f5e-49c9-ad9c-ef60a228ef53" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WaikikiBeachWalkRetailMember_d66057ec-0f81-46ef-9a7d-a48b8c314401" xlink:href="aat-20200331.xsd#aat_WaikikiBeachWalkRetailMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:to="loc_aat_WaikikiBeachWalkRetailMember_d66057ec-0f81-46ef-9a7d-a48b8c314401" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OutriggerHotelsAndResortsMember_38fb0034-92a1-4861-af3a-5e2e4494e0dd" xlink:href="aat-20200331.xsd#aat_OutriggerHotelsAndResortsMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:to="loc_aat_OutriggerHotelsAndResortsMember_38fb0034-92a1-4861-af3a-5e2e4494e0dd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WbwHotelLesseeLlcMember_49796b6a-bf15-45b0-af50-a1681fe992d3" xlink:href="aat-20200331.xsd#aat_WbwHotelLesseeLlcMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:to="loc_aat_WbwHotelLesseeLlcMember_49796b6a-bf15-45b0-af50-a1681fe992d3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_DelMonteCenterAffiliatesMember_ea4e5cc9-14be-4247-8841-d94adca9d8bd" xlink:href="aat-20200331.xsd#aat_DelMonteCenterAffiliatesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_38f34341-40b6-47f9-b58d-2d140bc4a233" xlink:to="loc_aat_DelMonteCenterAffiliatesMember_ea4e5cc9-14be-4247-8841-d94adca9d8bd" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LineOfCreditFutureTimePeriodAxis_45d364ce-9bbe-4925-a0b0-c90dda9b10f4" xlink:href="aat-20200331.xsd#aat_LineOfCreditFutureTimePeriodAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:to="loc_aat_LineOfCreditFutureTimePeriodAxis_45d364ce-9bbe-4925-a0b0-c90dda9b10f4" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LineOfCreditFutureTimePeriodDomain_45d364ce-9bbe-4925-a0b0-c90dda9b10f4_default" xlink:href="aat-20200331.xsd#aat_LineOfCreditFutureTimePeriodDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_aat_LineOfCreditFutureTimePeriodAxis_45d364ce-9bbe-4925-a0b0-c90dda9b10f4" xlink:to="loc_aat_LineOfCreditFutureTimePeriodDomain_45d364ce-9bbe-4925-a0b0-c90dda9b10f4_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:href="aat-20200331.xsd#aat_LineOfCreditFutureTimePeriodDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_aat_LineOfCreditFutureTimePeriodAxis_45d364ce-9bbe-4925-a0b0-c90dda9b10f4" xlink:to="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureYearPeriodOneMember_1f0624bc-8a5d-40e3-9ada-8aeea661ade9" xlink:href="aat-20200331.xsd#aat_FutureYearPeriodOneMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureYearPeriodOneMember_1f0624bc-8a5d-40e3-9ada-8aeea661ade9" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureYearPeriodTwoMember_db40856d-bf81-46b9-9402-00210c63b6db" xlink:href="aat-20200331.xsd#aat_FutureYearPeriodTwoMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureYearPeriodTwoMember_db40856d-bf81-46b9-9402-00210c63b6db" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureYearPeriodThreeMember_4d3b488f-7c10-4c54-b348-30b362254da7" xlink:href="aat-20200331.xsd#aat_FutureYearPeriodThreeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureYearPeriodThreeMember_4d3b488f-7c10-4c54-b348-30b362254da7" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureYearPeriodFourMember_87527a2d-8afe-4567-8d44-a3cf309d7689" xlink:href="aat-20200331.xsd#aat_FutureYearPeriodFourMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureYearPeriodFourMember_87527a2d-8afe-4567-8d44-a3cf309d7689" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureTimePeriodPriorMember_d80febb2-46f4-40db-a35b-99bd1bf430e9" xlink:href="aat-20200331.xsd#aat_FutureTimePeriodPriorMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureTimePeriodPriorMember_d80febb2-46f4-40db-a35b-99bd1bf430e9" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_FutureTimePeriodAfterMember_c9cd6ed8-eacb-458e-8808-b7e275b9857b" xlink:href="aat-20200331.xsd#aat_FutureTimePeriodAfterMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_LineOfCreditFutureTimePeriodDomain_bf9ba14e-1a98-4c0d-ad65-70d8702abe19" xlink:to="loc_aat_FutureTimePeriodAfterMember_c9cd6ed8-eacb-458e-8808-b7e275b9857b" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_926b09d8-4c69-4846-8329-cd876927e850" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:to="loc_srt_RangeAxis_926b09d8-4c69-4846-8329-cd876927e850" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_926b09d8-4c69-4846-8329-cd876927e850_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_926b09d8-4c69-4846-8329-cd876927e850" xlink:to="loc_srt_RangeMember_926b09d8-4c69-4846-8329-cd876927e850_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a57cd54b-298e-4778-a019-1fc279a9f4ab" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_926b09d8-4c69-4846-8329-cd876927e850" xlink:to="loc_srt_RangeMember_a57cd54b-298e-4778-a019-1fc279a9f4ab" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_41c793ed-d4d1-4439-b4b9-aa5c70b9fe25" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a57cd54b-298e-4778-a019-1fc279a9f4ab" xlink:to="loc_srt_MaximumMember_41c793ed-d4d1-4439-b4b9-aa5c70b9fe25" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c81e0d5b-7d21-4b8f-9b82-4575c30be192" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a57cd54b-298e-4778-a019-1fc279a9f4ab" xlink:to="loc_srt_MinimumMember_c81e0d5b-7d21-4b8f-9b82-4575c30be192" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4b3411cf-e396-4153-9691-61b2bd635995" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4b3411cf-e396-4153-9691-61b2bd635995" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_4b3411cf-e396-4153-9691-61b2bd635995_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4b3411cf-e396-4153-9691-61b2bd635995" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_4b3411cf-e396-4153-9691-61b2bd635995_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d64b13c7-296d-47fa-916c-be91fc6524b5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_4b3411cf-e396-4153-9691-61b2bd635995" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d64b13c7-296d-47fa-916c-be91fc6524b5" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_TotalRevenuesMember_5a8cffa6-a79f-48fa-8e6f-5eacf313c76f" xlink:href="aat-20200331.xsd#aat_TotalRevenuesMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_d64b13c7-296d-47fa-916c-be91fc6524b5" xlink:to="loc_aat_TotalRevenuesMember_5a8cffa6-a79f-48fa-8e6f-5eacf313c76f" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_502b7b3a-50fe-4738-9297-d749ab8a0d9d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_CommitmentAndContingenciesTable_9e1365f0-8d26-4024-9127-f9bc22ea1d67" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_502b7b3a-50fe-4738-9297-d749ab8a0d9d" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_502b7b3a-50fe-4738-9297-d749ab8a0d9d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_502b7b3a-50fe-4738-9297-d749ab8a0d9d" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_502b7b3a-50fe-4738-9297-d749ab8a0d9d_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_90a3a03e-7c12-47a3-8e6e-6bb5a6d590d9" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_502b7b3a-50fe-4738-9297-d749ab8a0d9d" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_90a3a03e-7c12-47a3-8e6e-6bb5a6d590d9" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RetailSegmentMember_cc0fe330-370d-49e0-b68a-8e6d0fd0729e" xlink:href="aat-20200331.xsd#aat_RetailSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_90a3a03e-7c12-47a3-8e6e-6bb5a6d590d9" xlink:to="loc_aat_RetailSegmentMember_cc0fe330-370d-49e0-b68a-8e6d0fd0729e" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OfficeSegmentMember_a0f512ed-49b8-40a6-a1b2-bf176c88b736" xlink:href="aat-20200331.xsd#aat_OfficeSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_90a3a03e-7c12-47a3-8e6e-6bb5a6d590d9" xlink:to="loc_aat_OfficeSegmentMember_a0f512ed-49b8-40a6-a1b2-bf176c88b736" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASES" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASES"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASES" xlink:type="extended" id="i5685ef7fdc224d61b4d350dc6565a048_LEASES"/>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESTables" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESTables" xlink:type="extended" id="i697bd914ff654e1bbd9349784c9826c4_LEASESTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESNarrativeDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESNarrativeDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESNarrativeDetails" xlink:type="extended" id="if1e6d53f582143278feac7a9c56e5b26_LEASESNarrativeDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LessorLeaseDescriptionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsMinimumTermRangeOfOfficeAndRetailLeases_358a8902-351c-4b1a-9320-bb7ede220b49" xlink:href="aat-20200331.xsd#aat_YearsMinimumTermRangeOfOfficeAndRetailLeases"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_YearsMinimumTermRangeOfOfficeAndRetailLeases_358a8902-351c-4b1a-9320-bb7ede220b49" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsMaximumTermRangeOfOfficeAndRetailLeases_ba9f3bc7-9973-44e3-8eb1-9e961d088749" xlink:href="aat-20200331.xsd#aat_YearsMaximumTermRangeOfOfficeAndRetailLeases"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_YearsMaximumTermRangeOfOfficeAndRetailLeases_ba9f3bc7-9973-44e3-8eb1-9e961d088749" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MonthsMinimumTermOfApartmentLeases_3bf216c8-37fe-4205-bf27-fe60349fd963" xlink:href="aat-20200331.xsd#aat_MonthsMinimumTermOfApartmentLeases"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_MonthsMinimumTermOfApartmentLeases_3bf216c8-37fe-4205-bf27-fe60349fd963" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MonthsMaximumTermLengthOfApartmentLeases_09b8942b-54f8-4c3f-a244-d63254eb9b0f" xlink:href="aat-20200331.xsd#aat_MonthsMaximumTermLengthOfApartmentLeases"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_MonthsMaximumTermLengthOfApartmentLeases_09b8942b-54f8-4c3f-a244-d63254eb9b0f" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OperatingLeasesRentalPeriodTerms_fdd470da-5a7d-4506-be1e-065a02318ae2" xlink:href="aat-20200331.xsd#aat_OperatingLeasesRentalPeriodTerms"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_OperatingLeasesRentalPeriodTerms_fdd470da-5a7d-4506-be1e-065a02318ae2" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_YearsLeaseExtensionOptionLength_e8332ec0-c3f5-4af2-a546-aecc8e6fb225" xlink:href="aat-20200331.xsd#aat_YearsLeaseExtensionOptionLength"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_YearsLeaseExtensionOptionLength_e8332ec0-c3f5-4af2-a546-aecc8e6fb225" xlink:type="arc" order="5"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LeaseExtensionOptionsExercisePeriod_77349423-f592-4365-8961-d2fd6eebc91a" xlink:href="aat-20200331.xsd#aat_LeaseExtensionOptionsExercisePeriod"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_aat_LeaseExtensionOptionsExercisePeriod_77349423-f592-4365-8961-d2fd6eebc91a" xlink:type="arc" order="6"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_caa0cd13-d2fd-41f9-949c-360a6dcfa13e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_caa0cd13-d2fd-41f9-949c-360a6dcfa13e" xlink:type="arc" order="7"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionTable_4f21e959-e51c-4ae8-85ae-7381addd6b55" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LessorLeaseDescriptionTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_47720c77-d83e-47ce-b03d-f606425668e5" xlink:to="loc_us-gaap_LessorLeaseDescriptionTable_4f21e959-e51c-4ae8-85ae-7381addd6b55" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_523ddef7-2fbd-4519-a765-c497f77d7429" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LessorLeaseDescriptionTable_4f21e959-e51c-4ae8-85ae-7381addd6b55" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_523ddef7-2fbd-4519-a765-c497f77d7429" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_523ddef7-2fbd-4519-a765-c497f77d7429_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_523ddef7-2fbd-4519-a765-c497f77d7429" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_523ddef7-2fbd-4519-a765-c497f77d7429_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_89118bc2-bcb0-4c39-a851-9d953b2023ac" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis_523ddef7-2fbd-4519-a765-c497f77d7429" xlink:to="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_89118bc2-bcb0-4c39-a851-9d953b2023ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LandMarkAtOneMarketMember_14529075-d055-4baf-b044-fa835119d422" xlink:href="aat-20200331.xsd#aat_LandMarkAtOneMarketMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PurchaseCommitmentExcludingLongtermCommitmentDomain_89118bc2-bcb0-4c39-a851-9d953b2023ac" xlink:to="loc_aat_LandMarkAtOneMarketMember_14529075-d055-4baf-b044-fa835119d422" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LessorLeaseDescriptionTable_4f21e959-e51c-4ae8-85ae-7381addd6b55" xlink:to="loc_srt_RangeAxis_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76" xlink:to="loc_srt_RangeMember_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_db1a8cfa-29b5-423e-9bbd-7134bcc13271" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fd11a1ec-57d4-4cfd-bddd-b0295b05bd76" xlink:to="loc_srt_RangeMember_db1a8cfa-29b5-423e-9bbd-7134bcc13271" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_23868870-bd5f-49e6-a8a9-efb82a0d4779" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_db1a8cfa-29b5-423e-9bbd-7134bcc13271" xlink:to="loc_srt_MinimumMember_23868870-bd5f-49e6-a8a9-efb82a0d4779" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_af73e18b-72be-4341-ab38-b9a0ce4f8d69" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_db1a8cfa-29b5-423e-9bbd-7134bcc13271" xlink:to="loc_srt_MaximumMember_af73e18b-72be-4341-ab38-b9a0ce4f8d69" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESMinimumFutureRentalsfromNoncancelableOperatingLeasesDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESMinimumFutureRentalsfromNoncancelableOperatingLeasesDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESMinimumFutureRentalsfromNoncancelableOperatingLeasesDetails" xlink:type="extended" id="i51210c040ad4429caad2e2a5aba18e01_LEASESMinimumFutureRentalsfromNoncancelableOperatingLeasesDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESLeaseObligationsMinimumFutureRentalPaymentsfromOperatingLeasesDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESLeaseObligationsMinimumFutureRentalPaymentsfromOperatingLeasesDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESLeaseObligationsMinimumFutureRentalPaymentsfromOperatingLeasesDetails" xlink:type="extended" id="i6e2d1fb444da4ca3a3b3c3b154be2cce_LEASESLeaseObligationsMinimumFutureRentalPaymentsfromOperatingLeasesDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESLeaseCostsAdditionalLeaseInformationDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESLeaseCostsAdditionalLeaseInformationDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESLeaseCostsAdditionalLeaseInformationDetails" xlink:type="extended" id="i54e52243afc743e08af77f49185318e7_LEASESLeaseCostsAdditionalLeaseInformationDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/LEASESSupplementalLeaseInformationDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#LEASESSupplementalLeaseInformationDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/LEASESSupplementalLeaseInformationDetails" xlink:type="extended" id="ifee05db795494922b1678324160bae1c_LEASESSupplementalLeaseInformationDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSE" xlink:type="simple" xlink:href="aat-20200331.xsd#COMPONENTSOFRENTALINCOMEANDEXPENSE"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSE" xlink:type="extended" id="i2a5aa354304e497e95b9bac7b01bf800_COMPONENTSOFRENTALINCOMEANDEXPENSE"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSETables" xlink:type="simple" xlink:href="aat-20200331.xsd#COMPONENTSOFRENTALINCOMEANDEXPENSETables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSETables" xlink:type="extended" id="i0a13923219b34611a53ea30d75792acf_COMPONENTSOFRENTALINCOMEANDEXPENSETables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEComponentofRentalIncomeDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#COMPONENTSOFRENTALINCOMEANDEXPENSEComponentofRentalIncomeDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEComponentofRentalIncomeDetails" xlink:type="extended" id="i1564d141a3094675a7925b7d76ba9c99_COMPONENTSOFRENTALINCOMEANDEXPENSEComponentofRentalIncomeDetails">
<link:loc xlink:type="locator" xlink:label="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:href="aat-20200331.xsd#aat_RentalIncomeLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_LeaseRentalIncome_3a6a0485-0e99-48a8-a103-87bd460944fd" xlink:href="aat-20200331.xsd#aat_LeaseRentalIncome"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_aat_LeaseRentalIncome_3a6a0485-0e99-48a8-a103-87bd460944fd" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseVariableLeaseIncome_b2587394-e832-440d-8b0b-a248e0b8da0c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseVariableLeaseIncome"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_us-gaap_OperatingLeaseVariableLeaseIncome_b2587394-e832-440d-8b0b-a248e0b8da0c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_75d1b15f-9da1-4ba4-bef1-c3c78382d8a3" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_75d1b15f-9da1-4ba4-bef1-c3c78382d8a3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OtherRealEstateRentalRevenue_fd0c0565-482b-419f-b5cc-011b7ba0f68d" xlink:href="aat-20200331.xsd#aat_OtherRealEstateRentalRevenue"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_aat_OtherRealEstateRentalRevenue_fd0c0565-482b-419f-b5cc-011b7ba0f68d" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_a03c9d36-5091-4584-9b05-c82774b7db65" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_a03c9d36-5091-4584-9b05-c82774b7db65" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RentalIncomeTable_f4777073-7a44-4fe0-bebf-91774d025278" xlink:href="aat-20200331.xsd#aat_RentalIncomeTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_aat_RentalIncomeLineItems_ac62ded4-1c4a-434e-80a7-04853715acd6" xlink:to="loc_aat_RentalIncomeTable_f4777073-7a44-4fe0-bebf-91774d025278" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_43ca7b84-7ff7-4e62-8b91-d3d675d514cb" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_aat_RentalIncomeTable_f4777073-7a44-4fe0-bebf-91774d025278" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_43ca7b84-7ff7-4e62-8b91-d3d675d514cb" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_43ca7b84-7ff7-4e62-8b91-d3d675d514cb_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_43ca7b84-7ff7-4e62-8b91-d3d675d514cb" xlink:to="loc_us-gaap_SegmentDomain_43ca7b84-7ff7-4e62-8b91-d3d675d514cb_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_43ca7b84-7ff7-4e62-8b91-d3d675d514cb" xlink:to="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RetailSegmentMember_9a7a45e5-d7fe-4f9c-8721-b4528c802ed0" xlink:href="aat-20200331.xsd#aat_RetailSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:to="loc_aat_RetailSegmentMember_9a7a45e5-d7fe-4f9c-8721-b4528c802ed0" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OfficeSegmentMember_620ce722-95ac-40ec-b349-0ee2f571efbb" xlink:href="aat-20200331.xsd#aat_OfficeSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:to="loc_aat_OfficeSegmentMember_620ce722-95ac-40ec-b349-0ee2f571efbb" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MultifamilySegmentMember_47c5e45b-2ef3-4a4a-9df1-85bfe2572364" xlink:href="aat-20200331.xsd#aat_MultifamilySegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:to="loc_aat_MultifamilySegmentMember_47c5e45b-2ef3-4a4a-9df1-85bfe2572364" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MixedUseSegmentMember_ff011c34-438a-46e5-843a-b0c3f51cd57b" xlink:href="aat-20200331.xsd#aat_MixedUseSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_34d73ad3-ec7f-4b65-b662-32a4ad18c97e" xlink:to="loc_aat_MixedUseSegmentMember_ff011c34-438a-46e5-843a-b0c3f51cd57b" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#COMPONENTSOFRENTALINCOMEANDEXPENSEDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEDetails" xlink:type="extended" id="if4551aa013cb4603b310b83dac76d7fe_COMPONENTSOFRENTALINCOMEANDEXPENSEDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEComponentsofRentalExpensesDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#COMPONENTSOFRENTALINCOMEANDEXPENSEComponentsofRentalExpensesDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/COMPONENTSOFRENTALINCOMEANDEXPENSEComponentsofRentalExpensesDetails" xlink:type="extended" id="i3eea15f3612a4aedb8a55251d9d4f786_COMPONENTSOFRENTALINCOMEANDEXPENSEComponentsofRentalExpensesDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHEREXPENSEINCOMENET" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHEREXPENSEINCOMENET"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHEREXPENSEINCOMENET" xlink:type="extended" id="if300201cb2ff422088a76c4b1c8f5eab_OTHEREXPENSEINCOMENET"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHEREXPENSEINCOMENETTables" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHEREXPENSEINCOMENETTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHEREXPENSEINCOMENETTables" xlink:type="extended" id="id94213fdec934a4d92e5f1d70bb3b423_OTHEREXPENSEINCOMENETTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/OTHEREXPENSEINCOMENETComponentsofOtherExpenseIncomeDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#OTHEREXPENSEINCOMENETComponentsofOtherExpenseIncomeDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/OTHEREXPENSEINCOMENETComponentsofOtherExpenseIncomeDetails" xlink:type="extended" id="i3411a8ab6ae44084b0e26989528162d2_OTHEREXPENSEINCOMENETComponentsofOtherExpenseIncomeDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/RELATEDPARTYTRANSACTIONS" xlink:type="simple" xlink:href="aat-20200331.xsd#RELATEDPARTYTRANSACTIONS"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/RELATEDPARTYTRANSACTIONS" xlink:type="extended" id="id51364fa6aa24befb835904def12f231_RELATEDPARTYTRANSACTIONS"/>
<link:roleRef roleURI="http://www.americanassets.com/role/RELATEDPARTYTRANSACTIONSDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#RELATEDPARTYTRANSACTIONSDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/RELATEDPARTYTRANSACTIONSDetails" xlink:type="extended" id="i46e1c65abd91420f9d2b4281eb4f7e0b_RELATEDPARTYTRANSACTIONSDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_20d77b1c-74f0-4349-aba4-83eb720ad801" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_d46dacbf-f0fd-4367-a910-67b29f8fd7ad" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_20d77b1c-74f0-4349-aba4-83eb720ad801" xlink:to="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_d46dacbf-f0fd-4367-a910-67b29f8fd7ad" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PercentageOfInvestmentInRelatedParty_dd2ca8f8-ac7c-4487-81c3-63ccca5d0107" xlink:href="aat-20200331.xsd#aat_PercentageOfInvestmentInRelatedParty"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_20d77b1c-74f0-4349-aba4-83eb720ad801" xlink:to="loc_aat_PercentageOfInvestmentInRelatedParty_dd2ca8f8-ac7c-4487-81c3-63ccca5d0107" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmountRecoveredForReimbursementsOfOperatingExpenseForRelatedParty_47bd41f8-6e09-4222-9fd8-ef39e4aa1720" xlink:href="aat-20200331.xsd#aat_AmountRecoveredForReimbursementsOfOperatingExpenseForRelatedParty"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_20d77b1c-74f0-4349-aba4-83eb720ad801" xlink:to="loc_aat_AmountRecoveredForReimbursementsOfOperatingExpenseForRelatedParty_47bd41f8-6e09-4222-9fd8-ef39e4aa1720" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_09d4796f-5153-45d4-a467-0c62b21bce19" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_20d77b1c-74f0-4349-aba4-83eb720ad801" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_09d4796f-5153-45d4-a467-0c62b21bce19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_CounterpartyNameAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_09d4796f-5153-45d4-a467-0c62b21bce19" xlink:to="loc_srt_CounterpartyNameAxis_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6_default" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d8cf5b0f-a23f-4aac-912a-60c72f0c33cd" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_b8312a0c-d616-4ad2-bf57-9b0adcea0bc6" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d8cf5b0f-a23f-4aac-912a-60c72f0c33cd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AAIAviationInc.Member_a5c038b3-952b-467c-957e-c3220edf6bcc" xlink:href="aat-20200331.xsd#aat_AAIAviationInc.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d8cf5b0f-a23f-4aac-912a-60c72f0c33cd" xlink:to="loc_aat_AAIAviationInc.Member_a5c038b3-952b-467c-957e-c3220edf6bcc" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0c1bd1e2-da10-4168-a725-396ee6928315" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_09d4796f-5153-45d4-a467-0c62b21bce19" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0c1bd1e2-da10-4168-a725-396ee6928315" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_0c1bd1e2-da10-4168-a725-396ee6928315_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0c1bd1e2-da10-4168-a725-396ee6928315" xlink:to="loc_us-gaap_RelatedPartyDomain_0c1bd1e2-da10-4168-a725-396ee6928315_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_72d1e72a-ac9f-40a2-a402-cf96ff51f33e" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_0c1bd1e2-da10-4168-a725-396ee6928315" xlink:to="loc_us-gaap_RelatedPartyDomain_72d1e72a-ac9f-40a2-a402-cf96ff51f33e" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_srt_BoardOfDirectorsChairmanMember_f4e210fb-f8b6-4f6d-9a21-dbeb88c6a454" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_BoardOfDirectorsChairmanMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_72d1e72a-ac9f-40a2-a402-cf96ff51f33e" xlink:to="loc_srt_BoardOfDirectorsChairmanMember_f4e210fb-f8b6-4f6d-9a21-dbeb88c6a454" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_WBWCHPLLCMember_f6172fcb-5877-4f8e-a6c8-30566840b348" xlink:href="aat-20200331.xsd#aat_WBWCHPLLCMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_72d1e72a-ac9f-40a2-a402-cf96ff51f33e" xlink:to="loc_aat_WBWCHPLLCMember_f6172fcb-5877-4f8e-a6c8-30566840b348" xlink:type="arc" order="1"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTING" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTING"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTING" xlink:type="extended" id="ib082b3ac6a794112b60776e401895c1d_SEGMENTREPORTING"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGTables" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGTables"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGTables" xlink:type="extended" id="i18ee0c7b33b64c90bdfdb2b96cc1103d_SEGMENTREPORTINGTables"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGDetails" xlink:type="extended" id="ibd9a1a89b730414b8d14496e70a46bcc_SEGMENTREPORTINGDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGOperatingActivityWithinReportableSegmentsDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGOperatingActivityWithinReportableSegmentsDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGOperatingActivityWithinReportableSegmentsDetails" xlink:type="extended" id="i279c757931e44678980f776ebc97c458_SEGMENTREPORTINGOperatingActivityWithinReportableSegmentsDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_ef705a69-5651-4c6e-8bf8-adeca6b8d40d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_ef705a69-5651-4c6e-8bf8-adeca6b8d40d" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_PropertyExpenses_8395a45e-bbb5-4e7a-bf82-5041c29b883f" xlink:href="aat-20200331.xsd#aat_PropertyExpenses"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:to="loc_aat_PropertyExpenses_8395a45e-bbb5-4e7a-bf82-5041c29b883f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_06adf052-d749-4b5b-96c2-9bd5a13ff9c8" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:to="loc_us-gaap_OperatingIncomeLoss_06adf052-d749-4b5b-96c2-9bd5a13ff9c8" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_d58dce8f-8259-4783-8deb-37994f247c4a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GrossProfit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:to="loc_us-gaap_GrossProfit_d58dce8f-8259-4783-8deb-37994f247c4a" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_40201336-7e4e-4c87-a54b-111112139c2d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_babccb9b-1f2c-4873-9490-2927d91d6882" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_40201336-7e4e-4c87-a54b-111112139c2d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_40201336-7e4e-4c87-a54b-111112139c2d" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a" xlink:to="loc_us-gaap_SegmentDomain_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9ae89732-e7d3-4b0c-acd4-1fd134daaa2a" xlink:to="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RetailSegmentMember_e8207964-d182-4ae6-8407-eed2fd45b8a5" xlink:href="aat-20200331.xsd#aat_RetailSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:to="loc_aat_RetailSegmentMember_e8207964-d182-4ae6-8407-eed2fd45b8a5" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OfficeSegmentMember_a2b477b3-31ad-4066-a256-24b5a5c77222" xlink:href="aat-20200331.xsd#aat_OfficeSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:to="loc_aat_OfficeSegmentMember_a2b477b3-31ad-4066-a256-24b5a5c77222" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MultifamilySegmentMember_7a05f2a9-9e4b-47f4-bfc5-670718973775" xlink:href="aat-20200331.xsd#aat_MultifamilySegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:to="loc_aat_MultifamilySegmentMember_7a05f2a9-9e4b-47f4-bfc5-670718973775" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MixedUseSegmentMember_b7895f39-c30f-42d2-9146-1f707fcc3d21" xlink:href="aat-20200331.xsd#aat_MixedUseSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fd78a8b2-48e6-4f07-a421-aecfb09d31ac" xlink:to="loc_aat_MixedUseSegmentMember_b7895f39-c30f-42d2-9146-1f707fcc3d21" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGReconciliationofSegmentProfittoNetIncomeAttributabletoStockholdersDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGReconciliationofSegmentProfittoNetIncomeAttributabletoStockholdersDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGReconciliationofSegmentProfittoNetIncomeAttributabletoStockholdersDetails" xlink:type="extended" id="i4788729a42c84dd39d375c2aa4130445_SEGMENTREPORTINGReconciliationofSegmentProfittoNetIncomeAttributabletoStockholdersDetails"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGNetRealEstateandSecuredNotePayableBalancesDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGNetRealEstateandSecuredNotePayableBalancesDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGNetRealEstateandSecuredNotePayableBalancesDetails" xlink:type="extended" id="i2ddc70791789409f9aaa42324c10ddb0_SEGMENTREPORTINGNetRealEstateandSecuredNotePayableBalancesDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_373ef505-77f9-4bea-a237-2eb65c675980" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_93bfb3fe-7b36-4195-8baa-0358cbb7de52" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_373ef505-77f9-4bea-a237-2eb65c675980" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_93bfb3fe-7b36-4195-8baa-0358cbb7de52" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayable_702c8ebc-27d0-4c90-9a50-c8be7c07dbf1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NotesPayable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_373ef505-77f9-4bea-a237-2eb65c675980" xlink:to="loc_us-gaap_NotesPayable_702c8ebc-27d0-4c90-9a50-c8be7c07dbf1" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_fb69acb8-0048-4270-988a-1d60dbb50003" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredFinanceCostsNet"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_373ef505-77f9-4bea-a237-2eb65c675980" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_fb69acb8-0048-4270-988a-1d60dbb50003" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a8f487fb-8490-4c77-8eb5-9148b1ff127c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_373ef505-77f9-4bea-a237-2eb65c675980" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a8f487fb-8490-4c77-8eb5-9148b1ff127c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_df0b3b0d-0e9a-48c2-9323-4de059d47730" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a8f487fb-8490-4c77-8eb5-9148b1ff127c" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_df0b3b0d-0e9a-48c2-9323-4de059d47730" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_df0b3b0d-0e9a-48c2-9323-4de059d47730_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_df0b3b0d-0e9a-48c2-9323-4de059d47730" xlink:to="loc_us-gaap_SegmentDomain_df0b3b0d-0e9a-48c2-9323-4de059d47730_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_df0b3b0d-0e9a-48c2-9323-4de059d47730" xlink:to="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RetailSegmentMember_2923769f-bb9d-4bc3-b93a-b074e8466766" xlink:href="aat-20200331.xsd#aat_RetailSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:to="loc_aat_RetailSegmentMember_2923769f-bb9d-4bc3-b93a-b074e8466766" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OfficeSegmentMember_7199b7ef-7056-4ef9-9f6f-5460dee197f6" xlink:href="aat-20200331.xsd#aat_OfficeSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:to="loc_aat_OfficeSegmentMember_7199b7ef-7056-4ef9-9f6f-5460dee197f6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MultifamilySegmentMember_73817f59-87eb-4e42-85fe-b7bf3b6ce4b3" xlink:href="aat-20200331.xsd#aat_MultifamilySegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:to="loc_aat_MultifamilySegmentMember_73817f59-87eb-4e42-85fe-b7bf3b6ce4b3" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MixedUseSegmentMember_14c9d9f3-775b-432e-bae3-e131becfe5e2" xlink:href="aat-20200331.xsd#aat_MixedUseSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_60eddf1a-e520-4818-a6d6-d100f076973d" xlink:to="loc_aat_MixedUseSegmentMember_14c9d9f3-775b-432e-bae3-e131becfe5e2" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a8f487fb-8490-4c77-8eb5-9148b1ff127c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7a67de3c-e4af-477e-8ba3-542ad829baab" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_4ac64fdf-cfc2-40c1-87c3-5f90ed40a2b1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7a67de3c-e4af-477e-8ba3-542ad829baab" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_a1d6e605-0698-4e8b-a77e-9d2765106520" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SecuredDebtMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_7a67de3c-e4af-477e-8ba3-542ad829baab" xlink:to="loc_us-gaap_SecuredDebtMember_a1d6e605-0698-4e8b-a77e-9d2765106520" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_ababbc9c-55fd-4303-9c3a-993be15b2e68" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a8f487fb-8490-4c77-8eb5-9148b1ff127c" xlink:to="loc_dei_LegalEntityAxis_ababbc9c-55fd-4303-9c3a-993be15b2e68" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_ababbc9c-55fd-4303-9c3a-993be15b2e68_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_ababbc9c-55fd-4303-9c3a-993be15b2e68" xlink:to="loc_dei_EntityDomain_ababbc9c-55fd-4303-9c3a-993be15b2e68_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_21db9a03-a3eb-494a-8d08-87c73aa822f6" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_ababbc9c-55fd-4303-9c3a-993be15b2e68" xlink:to="loc_dei_EntityDomain_21db9a03-a3eb-494a-8d08-87c73aa822f6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_06098930-2938-49b6-aea6-514b0275fcea" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_21db9a03-a3eb-494a-8d08-87c73aa822f6" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_06098930-2938-49b6-aea6-514b0275fcea" xlink:type="arc" order="0"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/SEGMENTREPORTINGCapitalExpendituresDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SEGMENTREPORTINGCapitalExpendituresDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SEGMENTREPORTINGCapitalExpendituresDetails" xlink:type="extended" id="ib243fc690d43482c8f2719aec46bee21_SEGMENTREPORTINGCapitalExpendituresDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_c5ecaddb-d5c6-48b2-90c8-4dd03003843b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_CapitalExpendituresandLeasingCommissions_d5022b9f-16a8-47dc-81dc-f6496dece794" xlink:href="aat-20200331.xsd#aat_CapitalExpendituresandLeasingCommissions"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c5ecaddb-d5c6-48b2-90c8-4dd03003843b" xlink:to="loc_aat_CapitalExpendituresandLeasingCommissions_d5022b9f-16a8-47dc-81dc-f6496dece794" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a4b5fcc4-3851-42ba-be2d-70ce76ace603" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_c5ecaddb-d5c6-48b2-90c8-4dd03003843b" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a4b5fcc4-3851-42ba-be2d-70ce76ace603" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_b6f2d42f-cf06-4c66-bd7f-79030caba44d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a4b5fcc4-3851-42ba-be2d-70ce76ace603" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_b6f2d42f-cf06-4c66-bd7f-79030caba44d" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b6f2d42f-cf06-4c66-bd7f-79030caba44d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6f2d42f-cf06-4c66-bd7f-79030caba44d" xlink:to="loc_us-gaap_SegmentDomain_b6f2d42f-cf06-4c66-bd7f-79030caba44d_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6f2d42f-cf06-4c66-bd7f-79030caba44d" xlink:to="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_RetailSegmentMember_3c9ce746-b6ec-4f52-873f-ad3428dc4ea1" xlink:href="aat-20200331.xsd#aat_RetailSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:to="loc_aat_RetailSegmentMember_3c9ce746-b6ec-4f52-873f-ad3428dc4ea1" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_OfficeSegmentMember_fed3dc75-3b8d-4ef8-bde7-49d60e40854f" xlink:href="aat-20200331.xsd#aat_OfficeSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:to="loc_aat_OfficeSegmentMember_fed3dc75-3b8d-4ef8-bde7-49d60e40854f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MultifamilySegmentMember_a7318f1b-50de-4b43-b0d4-ad56379a156b" xlink:href="aat-20200331.xsd#aat_MultifamilySegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:to="loc_aat_MultifamilySegmentMember_a7318f1b-50de-4b43-b0d4-ad56379a156b" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_MixedUseSegmentMember_f522de12-5801-4304-81e5-d9e28e3e9b32" xlink:href="aat-20200331.xsd#aat_MixedUseSegmentMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f02d9a3a-2527-4667-bffa-00a65cd705d6" xlink:to="loc_aat_MixedUseSegmentMember_f522de12-5801-4304-81e5-d9e28e3e9b32" xlink:type="arc" order="3"/>
</link:definitionLink>
<link:roleRef roleURI="http://www.americanassets.com/role/SUBSEQUENTEVENT" xlink:type="simple" xlink:href="aat-20200331.xsd#SUBSEQUENTEVENT"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUBSEQUENTEVENT" xlink:type="extended" id="i01635d61ed02456b82d43a9eb6ed4033_SUBSEQUENTEVENT"/>
<link:roleRef roleURI="http://www.americanassets.com/role/SUBSEQUENTEVENTDetails" xlink:type="simple" xlink:href="aat-20200331.xsd#SUBSEQUENTEVENTDetails"/>
<link:definitionLink xlink:role="http://www.americanassets.com/role/SUBSEQUENTEVENTDetails" xlink:type="extended" id="i140c3a9c3b1a4ff9b11a8788fd0bef77_SUBSEQUENTEVENTDetails">
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_23641322-43ec-4096-9fb4-f3cb5b62043d" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromUnsecuredLinesOfCredit_c5925ced-1f2e-4d4d-82e3-d7ed40b5f71b" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromUnsecuredLinesOfCredit"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_23641322-43ec-4096-9fb4-f3cb5b62043d" xlink:to="loc_us-gaap_ProceedsFromUnsecuredLinesOfCredit_c5925ced-1f2e-4d4d-82e3-d7ed40b5f71b" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_47356591-994e-4390-becd-107f3fb0b03c" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_23641322-43ec-4096-9fb4-f3cb5b62043d" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_47356591-994e-4390-becd-107f3fb0b03c" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTable"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_23641322-43ec-4096-9fb4-f3cb5b62043d" xlink:to="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_21d5dd51-7c29-44b9-9378-d076851e11fd" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_21d5dd51-7c29-44b9-9378-d076851e11fd" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_21d5dd51-7c29-44b9-9378-d076851e11fd_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_21d5dd51-7c29-44b9-9378-d076851e11fd" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_21d5dd51-7c29-44b9-9378-d076851e11fd_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_f8ea0b62-8400-4c4c-a716-5d3da7d4546f" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_21d5dd51-7c29-44b9-9378-d076851e11fd" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_f8ea0b62-8400-4c4c-a716-5d3da7d4546f" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_ab2c83e4-c3c9-41d5-911d-875e15553886" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_f8ea0b62-8400-4c4c-a716-5d3da7d4546f" xlink:to="loc_us-gaap_SubsequentEventMember_ab2c83e4-c3c9-41d5-911d-875e15553886" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_a0869915-2afb-4df0-84d8-7730f5d15b22" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:to="loc_us-gaap_DebtInstrumentAxis_a0869915-2afb-4df0-84d8-7730f5d15b22" xlink:type="arc" order="2"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a0869915-2afb-4df0-84d8-7730f5d15b22_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_a0869915-2afb-4df0-84d8-7730f5d15b22" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a0869915-2afb-4df0-84d8-7730f5d15b22_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3f0db640-1acc-48a7-a252-85a1ffb32baf" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_a0869915-2afb-4df0-84d8-7730f5d15b22" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3f0db640-1acc-48a7-a252-85a1ffb32baf" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_SecondAmendedandRestatedCreditFacilityMember_0a22f9b2-fa63-4268-9ccc-5e3dea11470d" xlink:href="aat-20200331.xsd#aat_SecondAmendedandRestatedCreditFacilityMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3f0db640-1acc-48a7-a252-85a1ffb32baf" xlink:to="loc_aat_SecondAmendedandRestatedCreditFacilityMember_0a22f9b2-fa63-4268-9ccc-5e3dea11470d" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_f74501c0-e459-4080-b542-992a771ce2e1" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_f74501c0-e459-4080-b542-992a771ce2e1" xlink:type="arc" order="3"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f74501c0-e459-4080-b542-992a771ce2e1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f74501c0-e459-4080-b542-992a771ce2e1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f74501c0-e459-4080-b542-992a771ce2e1_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_e7f9b3c3-e02f-4b02-9e8e-1645cf6204a7" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f74501c0-e459-4080-b542-992a771ce2e1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_e7f9b3c3-e02f-4b02-9e8e-1645cf6204a7" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_cfa240a6-7a38-4b0e-b33e-db34161b3596" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_e7f9b3c3-e02f-4b02-9e8e-1645cf6204a7" xlink:to="loc_us-gaap_LineOfCreditMember_cfa240a6-7a38-4b0e-b33e-db34161b3596" xlink:type="arc" order="0"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_c7e89302-94fa-4d87-90f0-47988fe3098a" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f7f5b3e8-9c61-4bf6-af0c-003182e54296" xlink:to="loc_dei_LegalEntityAxis_c7e89302-94fa-4d87-90f0-47988fe3098a" xlink:type="arc" order="4"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c7e89302-94fa-4d87-90f0-47988fe3098a_default" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_c7e89302-94fa-4d87-90f0-47988fe3098a" xlink:to="loc_dei_EntityDomain_c7e89302-94fa-4d87-90f0-47988fe3098a_default" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_d8284d53-ef64-48dc-84ae-18d1c8adc981" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_c7e89302-94fa-4d87-90f0-47988fe3098a" xlink:to="loc_dei_EntityDomain_d8284d53-ef64-48dc-84ae-18d1c8adc981" xlink:type="arc" order="1"/>
<link:loc xlink:type="locator" xlink:label="loc_aat_AmericanAssetsTrustL.P.Member_9ac49b11-dedd-4ae6-8769-0e7dd161710d" xlink:href="aat-20200331.xsd#aat_AmericanAssetsTrustL.P.Member"/>
<link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_d8284d53-ef64-48dc-84ae-18d1c8adc981" xlink:to="loc_aat_AmericanAssetsTrustL.P.Member_9ac49b11-dedd-4ae6-8769-0e7dd161710d" xlink:type="arc" order="0"/>
</link:definitionLink>
</link:linkbase>


6 Subsequent Filings that Reference this Filing

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

 1/19/21  American Assets Trust, L.P.       424B2       1/15/21    1:843K                                   Donnelley … Solutions/FA
 1/15/21  American Assets Trust, Inc.       424B7                  1:648K                                   Donnelley … Solutions/FA
 1/14/21  American Assets Trust, Inc.       424B7                  1:490K                                   Donnelley … Solutions/FA
 1/14/21  American Assets Trust, Inc.       S-3ASR      1/14/21    4:634K                                   Donnelley … Solutions/FA
 1/14/21  American Assets Trust, Inc.       S-3ASR      1/14/21    8:1M                                     Donnelley … Solutions/FA
 1/14/21  American Assets Trust, L.P.       424B2                  1:835K                                   Donnelley … Solutions/FA
Top
Filing Submission 0001500217-20-000037   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)

Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
AboutPrivacyRedactionsHelp — Tue., Apr. 30, 2:52:45.2am ET