<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-12-17</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001166789</issuerCik>
        <issuerName>LIN TV CORP.</issuerName>
        <issuerTradingSymbol>TVL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001375105</rptOwnerCik>
            <rptOwnerName>Blumenthal Scott M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LIN TV CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>ONE WEST EXCHANGE STREET, SUITE 5A</rptOwnerStreet2>
            <rptOwnerCity>PROVIDENCE</rptOwnerCity>
            <rptOwnerState>RI</rptOwnerState>
            <rptOwnerZipCode>02903</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive VP Television</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock (Restricted Stock)</value>
            </securityTitle>
            <transactionDate>
                <value>2012-12-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1234</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.8486</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>313689</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares sold pursuant to a 10b5-1 Plan. The sale price represents the weighted average sales price of individual sales totaling 1,234 shares in the aggregate.  The transactions occurred at prices in the range of $6.79 per share to $6.91 per share. Upon request from the Securities and Exchange Commission or a securityholder of the issuer, full information regarding the number of shares sold at each separate price will be made available.</footnote>
        <footnote id="F2">This number includes 193,816 restricted shares awarded pursuant to the Amended and Restated 2002 Stock Plan. These shares remain subject to forfeiture and are nontransferable until vested. The shares vest over either three (3), four (4) or five (5) years from the date of grant.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Nicholas N. Mohamed, Attorney-in-fact for Scott M. Blumenthal</signatureName>
        <signatureDate>2012-12-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
