The subject of the present invention is the use, for dyeing in particular human keratin materials, of a direct dye, in particular an azo dye, by dry thermal transfer. Its subject is furthermore a method for dyeing keratin materials, n which at least one direct dye, in particular one azo dye, contained in a dry composition, is applied to or close to the keratin materials, and a source of heat is applied, causing the thermal transfer of the direct dye(s) at the surface and/or inside the keratin materials. It relates furthermore to the dry composition and a method for preparing it.