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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

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

    <issuer>
        <issuerCik>0001500233</issuerCik>
        <issuerName>Ironwood Institutional Multi-Strategy Fund LLC</issuerName>
        <issuerTradingSymbol>N/A</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001749717</rptOwnerCik>
            <rptOwnerName>Phillips William John</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE MARKET PLAZA</rptOwnerStreet1>
            <rptOwnerStreet2>STEUART TOWER, SUITE 2500</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO,</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOther>true</isOther>
            <otherText>Officer of Investment Adviser</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Units</value>
            </securityTitle>
            <transactionDate>
                <value>2026-01-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>139.5423</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1289.9317</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>390.7463</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Values are given based on most recent calculated NAV per share (11/30/2025). Values at transaction date are not yet available.</footnote>
        <footnote id="F2">Reflects the purchase price on a per share basis. Prior Forms 4 filed by the reporting person on 3/3/2025 and 3/9/2021 reported the purchase price on an aggregate value basis, rather than on a per share basis, which has been adjusted to report such price on a per share basis as of this Form 4.</footnote>
        <footnote id="F3">Reflects the amount of securities beneficially owned by the reporting person once adjusted based on the final calculated NAV per share for the reporting person's purchase on 3/1/2025, which was reported on the Form 4 filed on 3/3/2025 based on the most recent calculated NAV per share available as of that date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ William John Phillips</signatureName>
        <signatureDate>2026-01-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
