A method is provided for dyeing a molded part produced in a 3D printing process with a polymer. The method includes a dyeing step for dyeing the surface of the molded part with a dye, and a first post-treatment step for fixing the dye which has penetrated the surface of the molded part. Optionally, a second post-treatment step can be carried out in order to achieve even better fixing of the dye which has penetrated the surface of the molded part.