<?xml version="1.0"?>
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        <issuerName>WESTMORELAND COAL Co</issuerName>
        <issuerTradingSymbol>WLB</issuerTradingSymbol>
    </issuer>

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            <rptOwnerName>Micheletti Joseph Earl</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>9540 SOUTH MAROON CIRCLE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
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            <isOfficer>1</isOfficer>
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            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
            <otherText></otherText>
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    <footnotes>
        <footnote id="F1">Each Restricted Stock Unit represents a contingent right to receive one share of common stock payable in common stock, cash or a combination thereof at the discretion of the Compensation and Benefits Committee.</footnote>
        <footnote id="F2">The Restricted Stock Units vest in three equal annual installments beginning on April 1st following the grant date.</footnote>
        <footnote id="F3">Each Performance Based Restricted Stock Unit (&quot;PBRSU&quot;) represents a contingent right to receive up to 1 .5 shares of common stock or the economic equivalent thereof. Units vest over three years and may become payable on April 1, 2020; achievement is 25% weighted based on a comparison of the company's relative total shareholder return (&quot;TSR&quot;) over the performance period to a weighted total shareholder return during such period of companies in the Russell 3000 Index; 25% weighted based on a comparison of the company's TSR over the performance period to a weighted TSR during such period of certain companies in the Market Vectors Global Coal Index with principal places of business in the US, Australia or Canada; and 50% weighted based on a three-year free cash flow goal for the Company's consolidated enterprise. For achievement between 100% and 150% of target performance, the PBRSU will be settled solely in cash.</footnote>
        <footnote id="F4">Each Cash Unit is settled solely in cash upon vesting and represents the economic equivalent of one share of the Issuer's common stock. These Cash Units vest in three equal installments on April 1, 2018, 2019 and 2020.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jennifer S. Grafton by Power of Attorney</signatureName>
        <signatureDate>2017-06-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2017-06-23
0
0000106455
WESTMORELAND COAL Co
WLB
0001521811
Micheletti Joseph Earl
9540 SOUTH MAROON CIRCLE
SUITE 300
ENGLEWOOD
CO
80112
0
1
0
0
Executive Vice President
Restricted Stock Units
2017-06-23
4
A
0
15853
A
2018-04-01
Common Stock
15853.0
15853
D
Performance Based Restricted Stock Units
2017-06-23
4
A
0
26421
A
2020-04-01
2020-04-01
Common Stock
26421.0
26421
D
Cash Units
2017-06-23
4
A
0
10568
A
2018-04-01
Common Stock
10568.0
10568
D
Each Restricted Stock Unit represents a contingent right to receive one share of common stock payable in common stock, cash or a combination thereof at the discretion of the Compensation and Benefits Committee.
The Restricted Stock Units vest in three equal annual installments beginning on April 1st following the grant date.
Each Performance Based Restricted Stock Unit ("PBRSU") represents a contingent right to receive up to 1 .5 shares of common stock or the economic equivalent thereof. Units vest over three years and may become payable on April 1, 2020; achievement is 25% weighted based on a comparison of the company's relative total shareholder return ("TSR") over the performance period to a weighted total shareholder return during such period of companies in the Russell 3000 Index; 25% weighted based on a comparison of the company's TSR over the performance period to a weighted TSR during such period of certain companies in the Market Vectors Global Coal Index with principal places of business in the US, Australia or Canada; and 50% weighted based on a three-year free cash flow goal for the Company's consolidated enterprise. For achievement between 100% and 150% of target performance, the PBRSU will be settled solely in cash.
Each Cash Unit is settled solely in cash upon vesting and represents the economic equivalent of one share of the Issuer's common stock. These Cash Units vest in three equal installments on April 1, 2018, 2019 and 2020.
/s/ Jennifer S. Grafton by Power of Attorney
2017-06-27