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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2021-08-16</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001633932</issuerCik>
        <issuerName>ESSA Pharma Inc.</issuerName>
        <issuerTradingSymbol>EPIX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001259869</rptOwnerCik>
            <rptOwnerName>BIOTECH GROWTH N V</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ARA HILL TOP BUILDING, UNIT A-5,</rptOwnerStreet1>
            <rptOwnerStreet2>PLETTERIJWEG OOST 1</rptOwnerStreet2>
            <rptOwnerCity>CURACAO</rptOwnerCity>
            <rptOwnerState>P8</rptOwnerState>
            <rptOwnerZipCode>00000</rptOwnerZipCode>
            <rptOwnerStateDescription>NETHERLANDS ANTILLES</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000924223</rptOwnerCik>
            <rptOwnerName>BB BIOTECH AG</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>SCHWERTSTRASSE 6</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SCHAFFHAUSEN</rptOwnerCity>
            <rptOwnerState>V8</rptOwnerState>
            <rptOwnerZipCode>CH-8200</rptOwnerZipCode>
            <rptOwnerStateDescription>SWITZERLAND</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4765814</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks>Biotech Growth N.V. is a wholly-owned subsidiary of BB Biotech AG. Accordingly, BB Biotech AG may be deemed to be the indirect beneficial owner of the securities of ESSA Pharma Inc. held directly or indirectly by Biotech Growth N.V. The Form 3 is jointly filed by BB Biotech AG and Biotech Growth N.V.</remarks>

    <ownerSignature>
        <signatureName>/s/ Martin Gubler</signatureName>
        <signatureDate>2021-08-16</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Daniel Koller</signatureName>
        <signatureDate>2021-08-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
