<?xml version="1.0" encoding="utf-8"?>
<!--Generated by DFIN XBRL Instance Document - http://www.dfinsolutions.com/ - Version R3.0 - on 23-March-2023 [10:07:58] {PM}-->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" 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">
  

  <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2022q4/ecd-2022q4.xsd#PvpAdjustmentsOnly" roleURI="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly"/>
  

  

  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  

  <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"/>
  

  <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"/>
  

  <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"/>
  

  <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"/>
  

  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll"/>
  

  <definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly">
    

    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2022q4/ecd-2022q4.xsd#ecd_AllAdjToCompMember" xlink:label="AllAdjToCompMember"/>
    

    <loc xlink:type="locator" xlink:href="hckt-20221231.xsd#hckt_ChangeInValueOfUnvestedEquityAwardsDuringRespectiveYearMember" xlink:label="ChangeInValueOfUnvestedEquityAwardsDuringRespectiveYearMember"/>
    

    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AllAdjToCompMember" xlink:to="ChangeInValueOfUnvestedEquityAwardsDuringRespectiveYearMember" order="100"/>
    

    <loc xlink:type="locator" xlink:href="hckt-20221231.xsd#hckt_ChangeInValueOfEquityAwardsVestedInRespectiveYearMember" xlink:label="ChangeInValueOfEquityAwardsVestedInRespectiveYearMember"/>
    

    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AllAdjToCompMember" xlink:to="ChangeInValueOfEquityAwardsVestedInRespectiveYearMember" order="101"/>
    

    <loc xlink:type="locator" xlink:href="hckt-20221231.xsd#hckt_MinusSctStockAwardsValueMember" xlink:label="MinusSctStockAwardsValueMember"/>
    

    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AllAdjToCompMember" xlink:to="MinusSctStockAwardsValueMember" order="102"/>
    

    <loc xlink:type="locator" xlink:href="hckt-20221231.xsd#hckt_PlusValueOfUnvestedEquityAwardsGrantedInRespectiveYearMember" xlink:label="PlusValueOfUnvestedEquityAwardsGrantedInRespectiveYearMember"/>
    

    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AllAdjToCompMember" xlink:to="PlusValueOfUnvestedEquityAwardsGrantedInRespectiveYearMember" order="103"/>
    

  </definitionLink>
  

  

</linkbase>
