The present invention provides a thermal transfer sheet including at least a transfer layer and a substrate. The transfer layer includes at least a protective layer adapted to be peelable from the substrate, and the transfer layer has a peel force in a non-heated state of 1 N/m or more and a peel force in a heated state of 10 N/m or less. The thermal transfer sheet exhibits a high level of adhesion therebetween, even when used in a compact printer that causes the thermal transfer sheet to be heated by the heat of a thermal head. The transfer layer exhibits a high level of releasability when being transferred.