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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2017-01-10</periodOfReport>

    <dateOfOriginalSubmission>2017-01-12</dateOfOriginalSubmission>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001679688</issuerCik>
        <issuerName>Colony NorthStar, Inc.</issuerName>
        <issuerTradingSymbol>CLNS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001076343</rptOwnerCik>
            <rptOwnerName>BARRACK THOMAS JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O COLONY NORTHSTAR, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>515 S. FLOWER STREET, 44TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Chairman</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>This amendment to the Initial Statement of Beneficial Ownership of Securities on Form 3, filed with the Securities and Exchange Commission on January 12, 2017, is being filed solely to amend the Power of Attorney filed as Exhibit 24.</remarks>

    <ownerSignature>
        <signatureName>/s/ David A. Palame, Attorney-in-Fact</signatureName>
        <signatureDate>2017-01-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
