A thermal transfer recording medium that is capable of dealing with the requirement for an increase in thermal transfer printing speed, and high density and high quality of a thermally transferred image, capable of preventing the occurrence of abnormal transfer at high temperature and high humidity, and capable of improving transfer sensitivity in printing. A thermal transfer recording medium includes a heat-resistant lubricating layer on one surface of a base material, and an undercoat layer and a dye layer in that order on the other surface of the base material. The undercoat layer includes a copolymer of a polyester having a sulfonic acid group and an acrylic polymer having at least one of a glycidyl group and a carboxyl group, polyvinylpyrrolidone, and an oxazoline group-containing polymer. A binder resin of the dye layer is an acid-modified polyvinyl acetoacetal resin.