<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/nport" xmlns:com="http://www.sec.gov/edgar/common" xmlns:ncom="http://www.sec.gov/edgar/nportcommon" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.sec.gov/edgar/nport eis_NPORT_Filer.xsd">
  <headerData>
    <submissionType>NPORT-P</submissionType>
    <isConfidential>false</isConfidential>
    <filerInfo>

      <filer>
        <issuerCredentials>
          <cik>0000067160</cik>
          <ccc>XXXXXXXX</ccc>
        </issuerCredentials>
      </filer>


      <seriesClassInfo>
        <seriesId>S000023210</seriesId>
        <classId>C000067576</classId>
      </seriesClassInfo>


    </filerInfo>
  </headerData>
  <formData>
    <genInfo>
      <regName>MML SERIES INVESTMENT FUND</regName>
      <regFileNumber>811-02224</regFileNumber>
      <regCik>0000067160</regCik>
      <regLei>VQ1HG47DNRJG3HBJH467</regLei>
      <regStreet1>1295 State Street</regStreet1>
      <regCity>Springfield</regCity>
      <regStateConditional regCountry="US" regState="US-MA"/>
      <regZipOrPostalCode>01111-0001</regZipOrPostalCode>
      <regPhone>413-744-1000</regPhone>
      <seriesName>MML American Funds Core Allocation Fund</seriesName>
      <seriesId>S000023210</seriesId>
      <seriesLei>549300RK1R4479LIXQ81</seriesLei>
      <repPdEnd>2025-12-31</repPdEnd>
      <repPdDate>2025-06-30</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>569870435.45</totAssets>
      <totLiabs>655406.84</totLiabs>
      <netAssets>569215028.61</netAssets>
      <assetsAttrMiscSec>0.00000000</assetsAttrMiscSec>
      <assetsInvested>0.00000000</assetsInvested>
      <amtPayOneYrBanksBorr>0.00000000</amtPayOneYrBanksBorr>
      <amtPayOneYrCtrldComp>0.00000000</amtPayOneYrCtrldComp>
      <amtPayOneYrOthAffil>0.00000000</amtPayOneYrOthAffil>
      <amtPayOneYrOther>0.00000000</amtPayOneYrOther>
      <amtPayAftOneYrBanksBorr>0.00000000</amtPayAftOneYrBanksBorr>
      <amtPayAftOneYrCtrldComp>0.00000000</amtPayAftOneYrCtrldComp>
      <amtPayAftOneYrOthAffil>0.00000000</amtPayAftOneYrOthAffil>
      <amtPayAftOneYrOther>0.00000000</amtPayAftOneYrOther>
      <delayDeliv>0.00000000</delayDeliv>
      <standByCommit>0.00000000</standByCommit>
      <liquidPref>0.00000000</liquidPref>
      <cshNotRptdInCorD>0.00000000</cshNotRptdInCorD>
      <isNonCashCollateral>N</isNonCashCollateral>
      <returnInfo>
        <monthlyTotReturns>
          <monthlyTotReturn classId="C000067576" rtn1="-0.37000000" rtn2="3.51000000" rtn3="3.74000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="138817.97000000" netUnrealizedAppr="-1924016.31000000"/>
        <othMon2 netRealizedGain="492311.49000000" netUnrealizedAppr="18919088.61000000"/>
        <othMon3 netRealizedGain="449124.68000000" netUnrealizedAppr="-18772037.16000000"/>
      </returnInfo>
      <mon1Flow redemption="9387777.22000000" reinvestment="0.00000000" sales="447229.98000000"/>
      <mon2Flow redemption="8618855.13000000" reinvestment="0.00000000" sales="672449.95000000"/>
      <mon3Flow redemption="9443455.35000000" reinvestment="0.00000000" sales="1317213.79000000"/>


    </fundInfo>
    <invstOrSecs>
      <invstOrSec>
        <name>American Funds Insurance Series - Washington Mutual Investors Fund</name>
        <lei>E8N96L3OLBC178UFN669</lei>
        <title>American Funds Insurance Series - Washington Mutual Investors Fund</title>
        <cusip>030372692</cusip>
        <identifiers>
          <isin value="US0303726923"/>
        </identifiers>
        <balance>9206116.37000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>157424589.88000000</valUSD>
        <pctVal>27.65643596312</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>AFIS Growth-Income Fund</name>
        <lei>UCVW0L2W23MYYH7ZDY46</lei>
        <title>AFIS Growth-Income Fund</title>
        <cusip>030372304</cusip>
        <identifiers>
          <isin value="US0303723045"/>
        </identifiers>
        <balance>2547890.55000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>158988370.26000000</valUSD>
        <pctVal>27.93116173482</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>American Funds Insurance Series - The Bond Fund Of America</name>
        <lei>FHEDDMKTP6L2RVHI1O58</lei>
        <title>American Funds Insurance Series - The Bond Fund Of America</title>
        <cusip>030372809</cusip>
        <identifiers>
          <isin value="US0303728093"/>
        </identifiers>
        <balance>20528171.30000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>196659881.03000000</valUSD>
        <pctVal>34.54931285110</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>International Fund/VIT</name>
        <lei>54P03CIVU00CG5WE6525</lei>
        <title>International Fund/VIT</title>
        <cusip>030372700</cusip>
        <identifiers>
          <isin value="US0303727004"/>
        </identifiers>
        <balance>2839879.71000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>56797594.28000000</valUSD>
        <pctVal>9.978231674363</pctVal>
        <payoffProfile>Long</payoffProfile>
        <assetCat>EC</assetCat>
        <issuerCat>RF</issuerCat>
        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
    </invstOrSecs>
    <explntrNotes>
      <explntrNote note="Monthly returns presented in Item B.5(a) have been calculated without deducting any applicable sales loads or redemption fees." noteItem="B.5.a"/>
    </explntrNotes>
    <signature>
      <ncom:dateSigned>2025-07-28</ncom:dateSigned>
      <ncom:nameOfApplicant>MML SERIES INVESTMENT FUND</ncom:nameOfApplicant>
      <ncom:signature>Renee Hitchcock</ncom:signature>
      <ncom:signerName>Renee Hitchcock</ncom:signerName>
      <ncom:title>CFO and Treasurer</ncom:title>
    </signature>
  </formData>
</edgarSubmission>
