An object of the present invention is provide a disperse dye composition that has the light fastness required of synthetic fiber materials for automotive interiors that are exposed to sunlight at high temperature and high humidity, and that has good blue, red, and yellow dyeability. This object is achieved by a mixed disperse dye composition comprising a blue disperse dye composition having a specific composition ratio of five specific types of disperse dyes, and other specific yellow and/or red disperse dyes. The invention makes it possible to provide a disperse dye composition having not only high fastness of each color but light fastness with a favorable balance of the three primary colors, with the dye properties of each color equal during dyeing, and good dye color reproducibility, as well as by a dyeing method using this dye.