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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-02-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001433269</issuerCik>
        <issuerName>Diligent Corp</issuerName>
        <issuerTradingSymbol>DIL.NZ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001438238</rptOwnerCik>
            <rptOwnerName>SPRING STREET PARTNERS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>488 MADISON AVENUE, 21ST FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001569612</rptOwnerCik>
            <rptOwnerName>West Broadway Advisors, L.L.C.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>488 MADISON AVENUE, 21ST FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-02-12</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5896973</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5896973</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Series A Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-02-12</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On February 12, 2016 the Issuer entered into a Merger Agreement (the &quot;Merger Agreement&quot;) among the Issuer and certain affiliates of Insight Venture Partners (&quot;Insight&quot;). In connection with the Merger Agreement, Spring Street Partners, L.P. (&quot;Spring Street&quot;) and certain of its affiliates entered into a Voting Agreement dated as of February 12, 2016 (the &quot;Voting Agreement&quot;) with an affiliate of Insight pursuant to which Spring Street and certain of its affiliates agreed to cause the shares of Common Stock and Series A Preferred Stock owned of record by Spring Street (the &quot;Subject Shares&quot;) to be voted in favor of the transactions contemplated by the Merger Agreement, subject to the terms and conditions set forth therein.</footnote>
        <footnote id="F2">West Broadway Advisors, L.L.C., as the sole general partner of Spring Street, may be deemed to have the shared power to vote or direct the vote and the shared power to dispose or direct the disposition of the Common Stock and Series A Preferred Stock owned of record by Spring Street. David J. Liptak, as the manager and sole member of West Broadway Advisors, L.L.C., may also be deemed to have the shared power to vote or direct the vote and the shared power to dispose or direct the disposition of the Subject Shares. Therefore, West Broadway Advisors, L.L.C. and David J. Liptak may be deemed to be the beneficial owners of the Subject Shares. West Broadway Advisors, L.L.C. and David J. Liptak each disclaim beneficial ownership of the Subject Shares except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F3">The shares of Series A Preferred Stock are convertible at any time on a one-for-one basis into Common Stock, subject to certain anti-dilution adjustments, and have no expiration date.</footnote>
    </footnotes>

    <remarks>This Form 4 is being filed jointly by (1) Spring Street Partners, L.P., a limited partnership organized under the Illinois Revised Uniform Limited Partnership Act of 1986 (&quot;Spring Street&quot;) and (ii) West Broadway Advisors, L.L.C., a limited liability company formed under the Delaware Limited Liability Company Act (each individually, a &quot;Reporting Person&quot; or collectively, the &quot;Reporting Persons&quot;). The Reporting Person may be deemed to be a director of the Issuer by virtue of David J. Liptak serving as its representative on the Issuer's board of directors. David Liptak is the sole member and manager of West Broadway Advisors, L.L.C.</remarks>

    <ownerSignature>
        <signatureName>/s/ Daniel T. Mongan, attorney-in-fact</signatureName>
        <signatureDate>2016-02-18</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Daniel T. Mongan, attorney-in-fact</signatureName>
        <signatureDate>2016-02-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
