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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-09-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001488075</issuerCik>
        <issuerName>IntraLinks Holdings, Inc.</issuerName>
        <issuerTradingSymbol>IL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001126022</rptOwnerCik>
            <rptOwnerName>RHO VENTURES IV QP LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001269066</rptOwnerCik>
            <rptOwnerName>RHO VENTURES IV GMBH &amp; CO BETEILIGUNGS KG</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001126016</rptOwnerCik>
            <rptOwnerName>RHO VENTURES IV LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001533275</rptOwnerCik>
            <rptOwnerName>Rho Ventures IV Holdings LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001269064</rptOwnerCik>
            <rptOwnerName>RHO MANAGEMENT VENTURES IV LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000943431</rptOwnerCik>
            <rptOwnerName>RUCH JOSHUA</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001120545</rptOwnerCik>
            <rptOwnerName>LESCHLY MARK</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001269068</rptOwnerCik>
            <rptOwnerName>RHO CAPITAL PARTNERS VERWALTUNGS GMBH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>152 WEST 57TH STREET, 23RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-09-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>27500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.5351</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3897935</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-09-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>17333</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.4927</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3880602</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Rho Ventures IV (QP), L.P.(&quot;RV QP&quot;) sold 9,339 shares, Rho Ventures IV GmbH &amp; Co. Beteiligungs KG (&quot;RV KG&quot;) sold 9,732 shares, Rho Ventures IV Holdings LLC (&quot;RV IV Holdings&quot;) sold 6,661 shares and Rho Ventures IV L.P. (&quot;RV IV LP&quot;) sold 1,768 shares.</footnote>
        <footnote id="F2">Consists of 1,323,762 shares held by RV QP, 1,379,554 shares held by RV KG, 944,154 shares held by RV IV Holdings and 250,465 shares held by RV IV LP.</footnote>
        <footnote id="F3">RV QP sold 5,886 shares, RV KG sold 6,134 shares, RV IV Holdings sold 4,198 shares and RV IV LP sold 1,115 shares.</footnote>
        <footnote id="F4">Consists of 1,317,876 shares held by RV QP, 1,373,420 shares held by RV KG, 939,956 shares held by RV IV Holdings and 249,350 shares held by RV IV LP.</footnote>
        <footnote id="F5">Rho Management Ventures IV, L.L.C. (&quot;RMV&quot;) is the general partner of RV QP and RV IV LP and the managing member of RV IV Holdings, and Rho Capital Partners Verwaltings GmbH (&quot;RCP Verwaltungs&quot;) is the general partner of RV KG. Each of RMV and RCP Verwaltungs disclaim beneficial ownership of the reportable securities and this report shall not be deemed an admission that RMV or RCP Verwaltungs is the beneficial owner of such securities, except to the extent of its pecuniary interest therein. Mark Leschly and Joshua Ruch are managing members of RMV and managing directors of RCP Verwaltungs. Each of Mark Leschly and Joshua Ruch disclaim beneficial ownership of the reportable securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities, except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jeffrey I. Martin Attorney in Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeffrey Martin Attorney In-fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeff I. Martin Attorney-In-Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/S/ Jeffrey I. Martin</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeff I. Martin Attorney-In-Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeffrey I. Martin Attorney-In-Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeffrey I. Martin, Attorney-In-Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Jeffrey I. Martin Attorney-In-Fact</signatureName>
        <signatureDate>2015-09-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
