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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-12-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000034563</issuerCik>
        <issuerName>FARMER BROTHERS CO</issuerName>
        <issuerTradingSymbol>FARM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001315366</rptOwnerCik>
            <rptOwnerName>Grossman Jeanne Farmer</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>FARMER BROS. CO.</rptOwnerStreet1>
            <rptOwnerStreet2>13601 NORTH FREEWAY, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>FORT WORTH</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>76177</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Trustee, Beneficiary, Settlor</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $1.00 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2016-12-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>851</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1206209</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Grant of restricted stock under the Farmer Bros. Co. Amended and Restated 2007 Long-Term Incentive Plan (&quot;Plan&quot;), granted on December 8, 2016; the restricted stock cliff vests on the first anniversary of the date of grant subject to continued service to Farmer Bros. Co. through the vesting date and the acceleration provisions of the Plan and restricted stock agreement.</footnote>
        <footnote id="F2">Reflects the reporting person's beneficial ownership of shares of Common Stock held in various family trusts of which Ms. Grossman is the sole trustee, co-trustee, beneficiary and/or settlor, as reported in the Company's Definitive Proxy Statement on Schedule 14A filed with the SEC on October 27, 2016, after giving effect to the reported transaction.</footnote>
    </footnotes>

    <remarks>Ex. 24 Power of Attorney attached.</remarks>

    <ownerSignature>
        <signatureName>/s/ Thomas J. Mattei, Jr., Attorney-In-Fact for Jeanne Farmer Grossman</signatureName>
        <signatureDate>2016-12-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
