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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-11-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000095953</issuerCik>
        <issuerName>ASCENT INDUSTRIES CO.</issuerName>
        <issuerTradingSymbol>ACNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001917701</rptOwnerCik>
            <rptOwnerName>Mazzaferro Aldo John Jr</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1400 16TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 270</rptOwnerStreet2>
            <rptOwnerCity>OAK BROOK</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60523</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-11-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>700</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>11.2057</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7312</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The reported price in column 4 is a weighted average purchase price. These shares were purchased in multiple transactions at prices ranging from $11.20 to $11.22 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth within this footnote.</footnote>
        <footnote id="F2">This amount includes 3,000 shares held in the reporting person's self directed IRA, after the transaction on November 11, 2022.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Doug Tackett, Power of Attorney for Aldo John Mazzaferro Jr</signatureName>
        <signatureDate>2022-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2022-11-11
0
0000095953
ASCENT INDUSTRIES CO.
ACNT
0001917701
Mazzaferro Aldo John Jr
1400 16TH STREET
SUITE 270
OAK BROOK
IL
60523
1
0
0
0
Common Stock
2022-11-11
4
P
0
700
11.2057
A
7312
D
The reported price in column 4 is a weighted average purchase price. These shares were purchased in multiple transactions at prices ranging from $11.20 to $11.22 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth within this footnote.
This amount includes 3,000 shares held in the reporting person's self directed IRA, after the transaction on November 11, 2022.
Doug Tackett, Power of Attorney for Aldo John Mazzaferro Jr
2022-11-14