Synonymized with Protambulyx eurycles by Clark, 1929, Proc. New Engl. zool. Club 11: 9. Listed as a species by Bridges, 1993, Cat. Fam. Gen. Spec. Sphingidae of the World: VIII.21. Resynonymized with Protambulyx eurycles by Kitching & Cadiou, 2000, Hawkmoths of the world: 64. Reinstated as a species by Haxaire & Mielke, 2020, European Ent. 11 (3+4): 121.
Protambulyx fasciatus differs from P. eurycles by the following characteres: smaller wingspan, forewing darker with the four antemedial and postmedial bands broader and diffuse; the oblique dark line on CuA1, wider and diffuse, while thin and well-defined in
P. eurycles. The female of P. fasciatus is greyish brown, slightly bigger than the male.