<?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>0001615735</rptOwnerCik>
            <rptOwnerName>Curtin Nancy Ann</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>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </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>
