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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-12-16</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001213980</issuerCik>
        <issuerName>EXCELSIOR BUYOUT INVESTORS LLC</issuerName>
        <issuerTradingSymbol>EBI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001364521</rptOwnerCik>
            <rptOwnerName>UST Advisers Inc.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>225 HIGH RIDGE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>STAMFORD,</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06905</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Investment Adviser</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>Due to certain restructurings of U.S. Trust Corporation's subsidiaries, UST Advisers, Inc. assumed all of the rights and liabilities of U.S. Trust Company, NA under the Investment Advisory Agreement and now serves as Investment Adviser to Excelsior Buyout Investors, LLC.</remarks>

    <ownerSignature>
        <signatureName>/s/ Raghav V. Nandagopal, Authorized Signatory</signatureName>
        <signatureDate>2006-08-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
