There are provided a thermal transfer film which can yield an image formed object possessing excellent fastness or resistance properties such as excellent abrasion resistance and lightfastness, has good sensitivity in transfer, and is free from blocking during storage in a roll form, a thermal transfer recording medium, and a method for image formation using them. The thermal transfer film comprises: a substrate; and one or a plurality of layers provided on one side of the substrate, the one or plurality of layers including at least a thermal transfer layer, the thermal transfer layer being located on the uppermost surface of the thermal transfer film, the thermal transfer layer comprising at least two polyester resins different from each other in number average molecular weigh.