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		<isConfidential>false</isConfidential>
		<filerInfo>

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

			<seriesClassInfo>
				<seriesId>S000034945</seriesId>
				<classId>C000107473</classId>
				<classId>C000107474</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>100 BRIGHT MEADOW BLVD.</regStreet1>
			<regCity>ENFIELD</regCity>
			<regStateConditional regCountry="US" regState="US-CT"/>
			<regZipOrPostalCode>06082-1981</regZipOrPostalCode>
			<regPhone>8605621000</regPhone>
			<seriesName>MML Focused Equity Fund</seriesName>
			<seriesId>S000034945</seriesId>
			<seriesLei>549300SLRZRGITT1HD33</seriesLei>
			<repPdEnd>2020-12-31</repPdEnd>
			<repPdDate>2020-03-31</repPdDate>
			<isFinalFiling>N</isFinalFiling>
		</genInfo>
		<fundInfo>
			<totAssets>270439159.91</totAssets>
			<totLiabs>961794.71</totLiabs>
			<netAssets>269477365.2</netAssets>
			<assetsAttrMiscSec>0</assetsAttrMiscSec>
			<assetsInvested>0</assetsInvested>
			<amtPayOneYrBanksBorr>0</amtPayOneYrBanksBorr>
			<amtPayOneYrCtrldComp>0</amtPayOneYrCtrldComp>
			<amtPayOneYrOthAffil>0</amtPayOneYrOthAffil>
			<amtPayOneYrOther>0</amtPayOneYrOther>
			<amtPayAftOneYrBanksBorr>0</amtPayAftOneYrBanksBorr>
			<amtPayAftOneYrCtrldComp>0</amtPayAftOneYrCtrldComp>
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			<amtPayAftOneYrOther>0</amtPayAftOneYrOther>
			<delayDeliv>0</delayDeliv>
			<standByCommit>0</standByCommit>
			<liquidPref>0</liquidPref>
			<cshNotRptdInCorD>40390.9</cshNotRptdInCorD>
			<borrowers>
				<borrower aggrVal="9135624.11" lei="1V8Y6QCX6YMJ2OELII46" name="CREDIT SUISSE SECURITIES (USA) LLC"/>
			</borrowers>
			<aggregateCondition isNonCashCollateral="Y">
				<aggregateInfos>
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						<invstCat>AMBS</invstCat>
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			<returnInfo>
				<monthlyTotReturns>
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					<monthlyTotReturn classId="C000107474" rtn1="-10.2" rtn2="-7.88" rtn3="1.07"/>
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				<monthlyReturnCats/>
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				<othMon2 netRealizedGain="1247206.29" netUnrealizedAppr="-26990411.14"/>
				<othMon3 netRealizedGain="409205.88" netUnrealizedAppr="2938483.78"/>
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			<mon3Flow redemption="3485189.1" reinvestment="0" sales="4435424.73"/>
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				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
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				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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				<name>BAXTER INTERNATIONAL INC</name>
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				<payoffProfile>Long</payoffProfile>
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				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
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			</invstOrSec>
			<invstOrSec>
				<name>CANADIAN NATL RAILWAY CO</name>
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				<title>COMMON STOCK</title>
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				<currencyConditional curCd="CAD" exchangeRt="1.4073"/>
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				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>CA</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>2</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
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			</invstOrSec>
			<invstOrSec>
				<name>CHUBB LTD</name>
				<lei>E0JAN6VLUDI1HITHT809</lei>
				<title>COMMON STOCK</title>
				<cusip>H1467J104</cusip>
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					<ticker value="CB"/>
					<other otherDesc="SEDOL Number" value="B3BQMF6"/>
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				<curCd>USD</curCd>
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				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>CH</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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			<invstOrSec>
				<name>COCA COLA CO/THE</name>
				<lei>UWJKFUJFZ02DKWI3RY53</lei>
				<title>COMMON STOCK USD.25</title>
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				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
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				<name>COLGATE PALMOLIVE CO</name>
				<lei>YMEGZFW4SBUSS5BQXF88</lei>
				<title>COMMON STOCK USD1.0</title>
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					<ticker value="CL"/>
					<other otherDesc="SEDOL Number" value="2209106"/>
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				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
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				<name>DANAHER CORP</name>
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				<curCd>USD</curCd>
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				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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				<name>DEERE + CO</name>
				<lei>PWFTNG3EI0Y73OXWDH08</lei>
				<title>COMMON STOCK USD1.0</title>
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				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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				<name>DIAGEO PLC</name>
				<lei>213800ZVIELEA55JMJ32</lei>
				<title>COMMON STOCK GBP.2893518</title>
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				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>GB</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>2</fairValLevel>
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			<invstOrSec>
				<name>GENERAL DYNAMICS CORP</name>
				<lei>9C1X8XOOTYY2FNYTVH06</lei>
				<title>COMMON STOCK USD1.0</title>
				<cusip>369550108</cusip>
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				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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			<invstOrSec>
				<name>JOHNSON + JOHNSON</name>
				<lei>549300G0CFPGEF6X2043</lei>
				<title>COMMON STOCK USD1.0</title>
				<cusip>478160104</cusip>
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				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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			<invstOrSec>
				<name>LINDE PLC</name>
				<lei>8945002PAZHZLBGKGF02</lei>
				<title>COMMON STOCK EUR.001</title>
				<cusip>G5494J103</cusip>
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				<curCd>USD</curCd>
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				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>IE</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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				<name>LOCKHEED MARTIN CORP</name>
				<lei>DPRBOZP0K5RM2YE8UU08</lei>
				<title>COMMON STOCK USD1.0</title>
				<cusip>539830109</cusip>
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					<ticker value="LMT"/>
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				<curCd>USD</curCd>
				<valUSD>5844175.9</valUSD>
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				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
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					<isNonCashCollateral>N</isNonCashCollateral>
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			<invstOrSec>
				<name>MARSH + MCLENNAN COS</name>
				<lei>549300XMP3KDCKJXIU47</lei>
				<title>COMMON STOCK USD1.0</title>
				<cusip>571748102</cusip>
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					<ticker value="MMC"/>
					<other otherDesc="SEDOL Number" value="2567741"/>
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				<curCd>USD</curCd>
				<valUSD>7315726.44</valUSD>
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				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
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					<isNonCashCollateral>N</isNonCashCollateral>
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			<invstOrSec>
				<name>MCDONALD S CORP</name>
				<lei>UE2136O97NLB5BYP9H04</lei>
				<title>COMMON STOCK USD.01</title>
				<cusip>580135101</cusip>
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					<other otherDesc="SEDOL Number" value="2550707"/>
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				<curCd>USD</curCd>
				<valUSD>13540180.8</valUSD>
				<pctVal>5.024607833</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>MEDTRONIC PLC</name>
				<lei>549300GX3ZBSQWUXY261</lei>
				<title>COMMON STOCK USD.1</title>
				<cusip>G5960L103</cusip>
				<identifiers>
					<isin value="IE00BTN1Y115"/>
					<ticker value="MDT"/>
					<other otherDesc="SEDOL Number" value="BTN1Y11"/>
				</identifiers>
				<balance>147378</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>13290548.04</valUSD>
				<pctVal>4.9319719414</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>IE</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>MICROSOFT CORP</name>
				<lei>INR2EJN1ERAN0W5ZP974</lei>
				<title>COMMON STOCK USD.00000625</title>
				<cusip>594918104</cusip>
				<identifiers>
					<isin value="US5949181045"/>
					<ticker value="MSFT"/>
					<other otherDesc="SEDOL Number" value="2588173"/>
				</identifiers>
				<balance>70573</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>11130067.83</valUSD>
				<pctVal>4.13024219</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>NIKE INC  CL B</name>
				<lei>787RXPR0UX0O0XUXPZ81</lei>
				<title>COMMON STOCK</title>
				<cusip>654106103</cusip>
				<identifiers>
					<isin value="US6541061031"/>
					<ticker value="NKE"/>
					<other otherDesc="SEDOL Number" value="2640147"/>
				</identifiers>
				<balance>161448</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>13358207.52</valUSD>
				<pctVal>4.9570796086</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>PEPSICO INC</name>
				<lei>FJSUNZKFNQ5YPJ5OT455</lei>
				<title>COMMON STOCK USD.017</title>
				<cusip>713448108</cusip>
				<identifiers>
					<isin value="US7134481081"/>
					<ticker value="PEP"/>
					<other otherDesc="SEDOL Number" value="2681511"/>
				</identifiers>
				<balance>102265</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>12282026.5</valUSD>
				<pctVal>4.5577210134</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>PNC FINANCIAL SERVICES GROUP</name>
				<lei>CFGNEKW0P8842LEUIA51</lei>
				<title>COMMON STOCK USD5.0</title>
				<cusip>693475105</cusip>
				<identifiers>
					<isin value="US6934751057"/>
					<ticker value="PNC"/>
					<other otherDesc="SEDOL Number" value="2692665"/>
				</identifiers>
				<balance>52523</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>5027501.56</valUSD>
				<pctVal>1.8656489224</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>PUBLIC STORAGE</name>
				<lei>549300LMZF40TKJ6DM64</lei>
				<title>REIT USD.1</title>
				<cusip>74460D109</cusip>
				<identifiers>
					<isin value="US74460D1090"/>
					<ticker value="PSA"/>
					<other otherDesc="SEDOL Number" value="2852533"/>
				</identifiers>
				<balance>39049</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>7755521.89</valUSD>
				<pctVal>2.8779863883</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>Repurchase Agreement</name>
				<lei>549300H47WTHXPU08X20</lei>
				<title>FIXED INC CLEARING CORP.REPO</title>
				<cusip>85748R009</cusip>
				<identifiers>
					<isin value="US85748R0096"/>
				</identifiers>
				<balance>8744463.03</balance>
				<units>PA</units>
				<curCd>USD</curCd>
				<valUSD>8744463.03</valUSD>
				<pctVal>3.2449712515</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>RA</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<repurchaseAgrmt>
					<transCat>Repurchase</transCat>
					<notClearedCentCparty isCleared="N">
						<counterpartyInfos>
							<counterpartyInfo lei="549300H47WTHXPU08X20" name="Fixed Income Clearing Corp."/>
						</counterpartyInfos>
					</notClearedCentCparty>
					<isTriParty>N</isTriParty>
					<repurchaseRt>0</repurchaseRt>
					<maturityDt>2020-04-01</maturityDt>
					<repurchaseCollaterals>
						<repurchaseCollateral>
							<principalAmt>8595000</principalAmt>
							<principalCd>USD</principalCd>
							<collateralVal>8923595.45</collateralVal>
							<collateralCd>USD</collateralCd>
							<invstCat>UST</invstCat>
						</repurchaseCollateral>
					</repurchaseCollaterals>
				</repurchaseAgrmt>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>TJX COMPANIES INC</name>
				<lei>V167QI9I69W364E2DY52</lei>
				<title>COMMON STOCK USD1.0</title>
				<cusip>872540109</cusip>
				<identifiers>
					<isin value="US8725401090"/>
					<ticker value="TJX"/>
					<other otherDesc="SEDOL Number" value="2989301"/>
				</identifiers>
				<balance>243032</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>11619359.92</valUSD>
				<pctVal>4.3118129463</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>UNION PACIFIC CORP</name>
				<lei>549300LMMRSZZCZ8CL11</lei>
				<title>COMMON STOCK USD2.5</title>
				<cusip>907818108</cusip>
				<identifiers>
					<isin value="US9078181081"/>
					<ticker value="UNP"/>
					<other otherDesc="SEDOL Number" value="2914734"/>
				</identifiers>
				<balance>66959</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>9443897.36</valUSD>
				<pctVal>3.5045234144</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>UNITEDHEALTH GROUP INC</name>
				<lei>549300GHBMY8T5GXDE41</lei>
				<title>COMMON STOCK USD.01</title>
				<cusip>91324P102</cusip>
				<identifiers>
					<isin value="US91324P1021"/>
					<ticker value="UNH"/>
					<other otherDesc="SEDOL Number" value="2917766"/>
				</identifiers>
				<balance>60114</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>14991229.32</valUSD>
				<pctVal>5.5630755143</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
			<invstOrSec>
				<name>VISA INC CLASS A SHARES</name>
				<lei>549300JZ4OKEHW3DPJ59</lei>
				<title>COMMON STOCK USD.0001</title>
				<cusip>92826C839</cusip>
				<identifiers>
					<isin value="US92826C8394"/>
					<ticker value="V"/>
					<other otherDesc="SEDOL Number" value="B2PZN04"/>
				</identifiers>
				<balance>32153</balance>
				<units>NS</units>
				<curCd>USD</curCd>
				<valUSD>5180491.36</valUSD>
				<pctVal>1.9224217055</pctVal>
				<payoffProfile>Long</payoffProfile>
				<assetCat>EC</assetCat>
				<issuerCat>CORP</issuerCat>
				<invCountry>US</invCountry>

				<isRestrictedSec>N</isRestrictedSec>

				<fairValLevel>1</fairValLevel>
				<securityLending>
					<isCashCollateral>N</isCashCollateral>
					<isNonCashCollateral>N</isNonCashCollateral>
					<isLoanByFund>N</isLoanByFund>
				</securityLending>
			</invstOrSec>
		</invstOrSecs>
		<signature>
			<ncom:dateSigned>2020-05-20</ncom:dateSigned>
			<ncom:nameOfApplicant>MML SERIES INVESTMENT FUND</ncom:nameOfApplicant>
			<ncom:signature>/s/ Renee Hitchcock</ncom:signature>
			<ncom:signerName>Renee Hitchcock</ncom:signerName>
			<ncom:title>Treasurer and CFO</ncom:title>
		</signature>
	</formData>
	<documents>XXXX</documents>
</edgarSubmission>
