There is provided a thermal transfer sheet that, by virtue of flexibility and heat resistance imparted by a primer layer constituting the thermal transfer sheet, is less likely to be broken even upon exposure to a high level of thermal energy and is highly suitable for high-speed printing. The thermal transfer sheet has a thermally transferable colorant layer provided on one surface of a base material sheet, and a heat-resistant slipping layer provided on the other surface of the base material sheet through a primer layer. The primer layer contains at least a polyvinyl alcohol resin and a crosslinking agent.