There is disclosed a method for forming a decorative metallic nitride coating on the surface of a substrate comprising the steps of disposing said substrate to be coated as a cathode in a material gas atmosphere at a pressure of 0.1 to 10 Torr, with said substrate maintained at a temperature of 200.degree. to 1000.degree. C., and applying a voltage of 200 to 8000 V to said substrate to prepare a direct current glow discharge space in the vicinity of said substrate, the improvement which comprises using as said material gas a mixed gas of a halide of titanium, zirconium or hafnium; hydrogen; and nitrogen, and controlling the current density of the electric current flowing through said substrate to be within the range of 0.01 to 1 mA/cm.sup.2.The method according to the present invention provides a uniform and beautiful metallic nitride coating which has a metallic luster stable with time, is excellent in mar resistance, and is suitable for decoration. Further, according to the method of this invention, a decorative metallic nitride coating capable of varying a tone on a metallic luster surface over a wide range can be formed.