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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-09-22</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000887591</issuerCik>
        <issuerName>FIBERMARK INC</issuerName>
        <issuerTradingSymbol>FMKIQ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001245461</rptOwnerCik>
            <rptOwnerName>MIDDLETON A DUNCAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>161 WELLINGTON RD.</rptOwnerStreet1>
            <rptOwnerStreet2>PO BOX 498</rptOwnerStreet2>
            <rptOwnerCity>BRATTLEBORO</rptOwnerCity>
            <rptOwnerState>VT</rptOwnerState>
            <rptOwnerZipCode>05302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Former President and Director</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <remarks>Mr. Middleton is no longer employed by FiberMark nor a member of the Board of Directors.</remarks>

    <ownerSignature>
        <signatureName>A. Duncan Middleton</signatureName>
        <signatureDate>2005-09-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
