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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-07-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001647088</issuerCik>
        <issuerName>WillScot Mobile Mini Holdings Corp.</issuerName>
        <issuerTradingSymbol>WSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001573194</rptOwnerCik>
            <rptOwnerName>Dial Sara R.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4646 E. VAN BUREN STREET,</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 400</rptOwnerStreet2>
            <rptOwnerCity>PHOENIX</rptOwnerCity>
            <rptOwnerState>AZ</rptOwnerState>
            <rptOwnerZipCode>85008</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock, par value $0.0001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2020-07-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>46178</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>46178</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Received in exchange for 19,201 shares of Mobile Mini, Inc. (&quot;Mobile Mini&quot;) common stock, par value $0.01 per share, in connection with the completion of the merger (the &quot;Merger&quot;), on July 1, 2020 (the &quot;Effective Date&quot;), of Picasso Merger Sub, Inc., a subsidiary of the Issuer, with and into Mobile Mini, pursuant to the Agreement and Plan of Merger, dated as of March 1, 2020, as amended on May 28, 2020. On the Effective Date, each share of Mobile Mini common stock was converted automatically into the right to receive 2.4050 shares of the Issuer's Class A common stock, par value $0.0001 per share, which was, immediately thereafter, reclassified as and converted into shares of the Issuer's common stock, par value $0.0001 per share.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Christopher J. Miner as Attorney-in-Fact</signatureName>
        <signatureDate>2020-07-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
