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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-02-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000752714</issuerCik>
        <issuerName>MCGRATH RENTCORP</issuerName>
        <issuerTradingSymbol>MGRC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001226137</rptOwnerCik>
            <rptOwnerName>HANNA JOSEPH F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MCGRATH RENTCORP</rptOwnerStreet1>
            <rptOwnerStreet2>5700 LAS POSITAS ROAD</rptOwnerStreet2>
            <rptOwnerCity>LIVERMORE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94551</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2026-02-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1300</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>169049</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents restricted stock units (&quot;RSUs&quot;).</footnote>
        <footnote id="F2">The RSUs were granted as consideration for Mr. Hanna's continuing role as a non-employee director of the Company in lieu of any executive officer award he would otherwise receive in 2026.  The RSUs were acquired under the 2016 Stock Incentive Plan. The restricted stock unit vest 100% on April 1, 2027. Each restricted stock unit represents a right to receive one share of stock or an amount equal to the fair market value of the common stock underlying the unit on the vesting date.</footnote>
        <footnote id="F3">Represents 167,049 shares outstanding and 1,300 unvested RSUs.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Gilda Malek, POA for Joseph Hanna</signatureName>
        <signatureDate>2026-03-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
