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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-01-02</periodOfReport>

    <issuer>
        <issuerCik>0001037976</issuerCik>
        <issuerName>JONES LANG LASALLE INC</issuerName>
        <issuerTradingSymbol>JLL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001514963</rptOwnerCik>
            <rptOwnerName>Bague Hugo</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>RIED 20</rptOwnerStreet1>
            <rptOwnerStreet2>6430 SCHWYZ</rptOwnerStreet2>
            <rptOwnerCity></rptOwnerCity>
            <rptOwnerState>V8</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription>SWITZERLAND</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-01-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>85</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>27625</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares elected to receive in lieu of annual cash retainer payable quarterly in advance for the first quarter of the fiscal year 2026, in accordance with prior election under the non-executive director compensation program. The receipt of these shares has been deferred pursuant to the Jones Lang LaSalle Inc Deferred Compensation Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Alan K. Tse, attorney-in-fact for Hugo Bague</signatureName>
        <signatureDate>2026-01-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
