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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-06-11</periodOfReport>

    <issuer>
        <issuerCik>0001744494</issuerCik>
        <issuerName>ADVENT TECHNOLOGIES HOLDINGS, INC.</issuerName>
        <issuerTradingSymbol>ADN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001843738</rptOwnerCik>
            <rptOwnerName>Coffey James F.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ADVENT TECHNOLOGIES HOLDINGS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>200 CLARENDON STREET</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>true</isOfficer>
            <officerTitle>COO and General Counsel</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2021-06-11</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2021-02-04</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>345794</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>936499</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>10.36</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-06-11</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2021-02-04</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>345794</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2022-02-04</value>
            </exerciseDate>
            <expirationDate>
                <value>2031-06-11</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>345794</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>345794</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 345,794 restricted stock units that is a contingent right to receive common stock upon vesting granted pursuant to the Advent Technologies Holdings, Inc. 2021 Equity Incentive Plan, dated as of February 4, 2021. The restricted stock units will vest 25% upon each anniversary of February 4, 2021, the vesting commencement date, until the fourth anniversary of the vesting commencement date.</footnote>
        <footnote id="F2">Received pursuant to the Advent Technologies Holdings, Inc. 2021 Equity Incentive Plan, dated as of February 4, 2021. The options will vest 25% upon each anniversary of February 4, 2021, the vesting commencement date, until the fourth anniversary of the vesting commencement date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>By: /s/ James F. Coffey</signatureName>
        <signatureDate>2021-06-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
