<?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>S000018540</seriesId>
        <classId>C000051436</classId>
        <classId>C000067779</classId>
      </seriesClassInfo>


    </filerInfo>
  </headerData>
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    <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 VIP Balanced Allocation Fund</seriesName>
      <seriesId>S000018540</seriesId>
      <seriesLei>54930063OMLROMEWP985</seriesLei>
      <repPdEnd>2026-12-31</repPdEnd>
      <repPdDate>2026-06-30</repPdDate>
      <isFinalFiling>N</isFinalFiling>
    </genInfo>
    <fundInfo>
      <totAssets>260105235.24</totAssets>
      <totLiabs>212215.06</totLiabs>
      <netAssets>259893020.18</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="C000051436" rtn1="4.28000000" rtn2="2.00000000" rtn3="0.00000000"/>
          <monthlyTotReturn classId="C000067779" rtn1="4.22000000" rtn2="1.92000000" rtn3="0.10000000"/>
        </monthlyTotReturns>
        <othMon1 netRealizedGain="-566061.22000000" netUnrealizedAppr="11533123.79000000"/>
        <othMon2 netRealizedGain="224498.83000000" netUnrealizedAppr="4929789.70000000"/>
        <othMon3 netRealizedGain="-150199.41000000" netUnrealizedAppr="288684.57000000"/>
      </returnInfo>
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      <mon2Flow redemption="5888336.45000000" reinvestment="0.00000000" sales="1040379.73000000"/>
      <mon3Flow redemption="4085112.52000000" reinvestment="0.00000000" sales="175876.70000000"/>


    </fundInfo>
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        <name>Invesco Global Strategic Income Fund</name>
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        <title>Invesco Global Strategic Income Fund</title>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
      <invstOrSec>
        <name>MML INTERNATIONAL EQUITY FUND</name>
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        <title>MML INTERNATIONAL EQUITY FUND</title>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
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        <name>MML FUNDAMENTAL GROWTH FUND</name>
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        <fairValLevel>1</fairValLevel>
        <securityLending>
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      </invstOrSec>
      <invstOrSec>
        <name>MML FOCUSED EQUITY FUND</name>
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        <fairValLevel>1</fairValLevel>
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          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MML SMALL CAP GROWTH EQUITY FD</name>
        <lei>HQ4SSOSDU7DRRXL6HW28</lei>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
      <invstOrSec>
        <name>MML TOTAL RETURN BOND FUND</name>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
      <invstOrSec>
        <name>MML SMALL COMPANY VALUE FUND</name>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
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        <name>MML GLOBAL FD</name>
        <lei>8T9HINFCQAU4P1AO8856</lei>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
      <invstOrSec>
        <name>MML SMALL/MID CAP VALUE</name>
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        <fairValLevel>1</fairValLevel>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
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        <name>MML BLUE CHIP GROWTH FD</name>
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        <name>MML INCOME AND GROWTH FD</name>
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      </invstOrSec>
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        <name>MML MANAGED BOND FUND</name>
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        <fairValLevel>1</fairValLevel>
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      </invstOrSec>
      <invstOrSec>
        <name>MML SER INVT FD II</name>
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        <invCountry>US</invCountry>
        <isRestrictedSec>N</isRestrictedSec>

        <fairValLevel>1</fairValLevel>
        <securityLending>
          <isCashCollateral>N</isCashCollateral>
          <isNonCashCollateral>N</isNonCashCollateral>
          <isLoanByFund>N</isLoanByFund>
        </securityLending>
      </invstOrSec>
      <invstOrSec>
        <name>MML SHORT DURATION BOND FUND</name>
        <lei>XL07OZJZFFLZ255H7071</lei>
        <title>MML SHORT DURATION BOND FUND</title>
        <cusip>55312G754</cusip>
        <identifiers>
          <isin value="US55312G7549"/>
        </identifiers>
        <balance>1080093.45000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>10088072.83000000</valUSD>
        <pctVal>3.881625148306</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>MML Barings High Yield Fund</name>
        <lei>AQDRLVGKF0IT8SWIC757</lei>
        <title>MML Barings High Yield Fund</title>
        <cusip>57629H327</cusip>
        <identifiers>
          <isin value="US57629H3277"/>
        </identifiers>
        <balance>92892.42000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>753357.52000000</valUSD>
        <pctVal>0.289872163353</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>PIMCO Variable Insurance Trust - Long-Term U.S. Government Portfolio</name>
        <lei>1HF6TMDVSLQTVB8TF611</lei>
        <title>PIMCO Variable Insurance Trust - Long-Term U.S. Government Portfolio</title>
        <cusip>693394710</cusip>
        <identifiers>
          <isin value="US6933947102"/>
        </identifiers>
        <balance>506002.30000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>3734296.97000000</valUSD>
        <pctVal>1.436859276718</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>Fidelity VIP Emerging Markets Portfolio</name>
        <lei>N/A</lei>
        <title>Fidelity VIP Emerging Markets Portfolio</title>
        <cusip>922177324</cusip>
        <identifiers>
          <isin value="US9221773248"/>
        </identifiers>
        <balance>215532.27000000</balance>
        <units>NS</units>
        <curCd>USD</curCd>
        <valUSD>4334353.95000000</valUSD>
        <pctVal>1.667745423481</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>2026-07-15</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>
