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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-07-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001584207</issuerCik>
        <issuerName>OneMain Holdings, Inc.</issuerName>
        <issuerTradingSymbol>OMF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001782937</rptOwnerCik>
            <rptOwnerName>Chadha Rajive</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ONEMAIN HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>601 N.W. SECOND STREET</rptOwnerStreet2>
            <rptOwnerCity>EVANSVILLE</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>47708</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>COO and EVP</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2019-07-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>18278</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18278</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Consists of employee restricted stock units (RSUs) granted under the OneMain Holdings, Inc. Amended and Restated 2013 Omnibus Incentive Plan.  The RSUs vest as follows: 1,621 RSUs on April 20, 2020, 7,813 RSUs on April 20, 2021 and 8,844 RSUs on April 20, 2022, subject to the reporting person's continued employment through the specified vesting date.   The reporting person will receive one share of common stock for each vested restricted stock unit.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jack R. Erkilla attorney-in-fact for Rajive Chadha</signatureName>
        <signatureDate>2019-07-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
