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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-02-28</periodOfReport>

    <issuer>
        <issuerCik>0001745916</issuerCik>
        <issuerName>PennyMac Financial Services, Inc.</issuerName>
        <issuerTradingSymbol>PFSI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001025424</rptOwnerCik>
            <rptOwnerName>ELBAUM MARK</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PENNYMAC FINANCIAL SERVICES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>3043 TOWNSGATE ROAD</rptOwnerStreet2>
            <rptOwnerCity>WESTLAKE VILLAGE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91361</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Chief Capital Markets Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-02-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>71</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>91.93</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5333</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares sold upon vesting of restricted share units.</footnote>
        <footnote id="F2">The reported amount consists of 3,492 of restricted stock units and 1,841 shares of Common Stock.  The restricted stock units are to be settled in an equal number of shares of Common Stock upon vesting.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Derek W. Stark, attorney-in-fact for Mr. Elbaum</signatureName>
        <signatureDate>2026-03-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
