Sphincterodiplostomum musculosum Dubois, 1936 (Diplostomidae, Diplostominae) was originally described on the basis of specimens collected from the intestine of agami heron, Agamia agami (Gmelin) (Ardeidae), in Mato Grosso, Brazil. The original description of this species was brief because it was based on a few immature specimens. The purpose of this paper is to describe the detailed morphological study of several adult specimens of S. musculosum obtained from the intestine of the great egret, Ardea alba L. (Ardeidae), from Argentina which revealed new characters. This represents a new host record and a new record in birds in Argentina.