To provide a thermal transfer sheet having a back layer excellent in heat resistance and slipping properties and causing no wrinkling at printing and no image-defect by tailing, the sheet being able to be prepared without a heat treating, such as aging.A thermal transfer sheet, comprising a substrate film, a transfer ink layer formed on one face thereof, and a back layer formed on the other face thereof, wherein the back layer comprises: a mixed binder containing a polyamide-imide resin (A) having a Tg of 200° C. or higher as determined by differential thermal analysis and a polyamide-imide silicone resin (B) having a Tg of 200° C. or higher; a mixture of a polyvalent metal salt of alkylphosphoric ester (C) and a metal salt of alkylcarboxylic acid (D), a silicone oil (E); and an inorganic filler (F).