<SEC-DOCUMENT>0001213809-19-000049.txt : 20190627
<SEC-HEADER>0001213809-19-000049.hdr.sgml : 20190627
<ACCEPTANCE-DATETIME>20190627181316
ACCESSION NUMBER:		0001213809-19-000049
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20190625
FILED AS OF DATE:		20190627
DATE AS OF CHANGE:		20190627

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Tarnok Michael P.
		CENTRAL INDEX KEY:			0001413525

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32513
		FILM NUMBER:		19926700

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		(212) 531-5965

	MAIL ADDRESS:	
		STREET 1:		KERYX BIOPHARMACEUTICALS, INC.
		STREET 2:		750 LEXINGTON AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DYADIC INTERNATIONAL INC
		CENTRAL INDEX KEY:			0001213809
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL ORGANIC CHEMICALS [2860]
		IRS NUMBER:				450486747
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		140 INTRACOASTAL POINTE DRIVE
		STREET 2:		SUITE 404
		CITY:			JUPITER
		STATE:			FL
		ZIP:			33477
		BUSINESS PHONE:		561-743-8333

	MAIL ADDRESS:	
		STREET 1:		140 INTRACOASTAL POINTE DRIVE
		STREET 2:		SUITE 404
		CITY:			JUPITER
		STATE:			FL
		ZIP:			33477

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CCP WORLDWIDE INC
		DATE OF NAME CHANGE:	20030110
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_156167358127165.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-06-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001213809</issuerCik>
        <issuerName>DYADIC INTERNATIONAL INC</issuerName>
        <issuerTradingSymbol>DYAI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001413525</rptOwnerCik>
            <rptOwnerName>Tarnok Michael P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>140 INTRACOASTAL POINTE DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 404</rptOwnerStreet2>
            <rptOwnerCity>JUPITER</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33477-5094</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>5.83</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-06-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2020-06-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2029-06-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael Tarnok</signatureName>
        <signatureDate>2019-06-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
