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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-11-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001126234</issuerCik>
        <issuerName>NEWLINK GENETICS CORP</issuerName>
        <issuerTradingSymbol>NLNK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001531178</rptOwnerCik>
            <rptOwnerName>Edick Paul R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O NEWLINK GENETICS CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>2503 SOUTH LOOP DR., SUITE 5100</rptOwnerStreet2>
            <rptOwnerCity>AMES</rptOwnerCity>
            <rptOwnerState>IA</rptOwnerState>
            <rptOwnerZipCode>50010</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>13.3</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-11-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>9522</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-11-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9522</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9522</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Automatic grant to the Reporting Person of a nonstatutory stock option under the Issuer's 2010 Non-Employee Directors' Stock Award Plan (the &quot;Plan&quot;).  The option vests over a two-year period, with 50% of the option vesting on November 2, 2013 and the remaining 50% of such option vesting in equal monthly installments over the next 12 months, provided (i) that the option shall vest in full on the date of the Annual Meeting held two years after the date of grant and (ii) that at the relevant vesting dates the Reporting Person's continuous service to the Issuer has not been terminated as defined in or as determined under the Plan.  The option expires ten years after the date of grant.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Gordon Link, by power of attorney</signatureName>
        <signatureDate>2012-11-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
