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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-03-06</periodOfReport>

    <issuer>
        <issuerCik>0001544229</issuerCik>
        <issuerName>Engility Holdings, Inc.</issuerName>
        <issuerTradingSymbol>EGL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001552713</rptOwnerCik>
            <rptOwnerName>Reed Craig R.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ENGILITY HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>3750 CENTERVIEW DRIVE</rptOwnerStreet2>
            <rptOwnerCity>CHANTILLY</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>20151</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP, Strategy &amp; Corporate Dev</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>308</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>34.02</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60060</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Reflects shares withheld to cover the payment of taxes following the vesting of the restricted stock units.</footnote>
        <footnote id="F2">On February 26, 2015, Engility Holdings, Inc. (f/k/a New East Holdings, Inc.) (&quot;New Engility&quot;) became the successor of Engility Holdings, Inc. (&quot;Engility&quot;) pursuant to the merger of Engility with and into New Engility, with New Engility continuing as the surviving corporation in the merger and changing its name to &quot;Engility Holdings, Inc.&quot; (the &quot;Engility Merger&quot;). The Engility Merger did not alter the proportionate interests of existing Engility security holders.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jon Brooks as Attorney-in-Fact</signatureName>
        <signatureDate>2015-03-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
