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

    <schemaVersion>X0407</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-05-10</periodOfReport>

    <issuer>
        <issuerCik>0001210677</issuerCik>
        <issuerName>FIRST ADVANTAGE CORP</issuerName>
        <issuerTradingSymbol>FA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001398537</rptOwnerCik>
            <rptOwnerName>Jardine Bret T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FIRST ADVANTAGE CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>1 CONCOURSE PARKWAY NE, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30328</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>See Remarks</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4378</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.61</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2023-05-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>64607</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2030-01-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>64607</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>162186</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes shares acquired under the Employee Stock Purchase Plan of First Advantage Corporation.</footnote>
        <footnote id="F2">The reporting person currently owns 64,607 previously unreported stock options, subject to time- and performance-based vesting criteria. Effective as of May 10, 2023, the Company's Board of Directors approved a modification of the vesting terms of unvested and unearned performance-based awards (the &quot;Modification&quot;). The Modification adds incremental vesting criteria to such stock options, which allows the following number of such stock options to vest, based solely on time, as follows, subject to continued service through such date: 12,921 options on January 31, 2024, 25,843 options on January 31, 2025, and 25,843 options on January 31, 2026, while preserving the eligibility to vest earlier upon a future &quot;Realization Event&quot; (as that term is defined in the relevant award agreement). As a result, 100% of such stock options will be vested on January 31, 2026 even if no Realization Event occurs prior to such date.</footnote>
        <footnote id="F3">Includes 97,597 previously reported time-based stock options, with the 32,438 remaining unvested time-based stock options scheduled to vest in equal installments on January 31, 2024 and 2025.</footnote>
    </footnotes>

    <remarks>Title: EVP, General Counsel &amp; Secretary</remarks>

    <ownerSignature>
        <signatureName>/s/ Bret T. Jardine</signatureName>
        <signatureDate>2023-05-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
