As part of an on-going study of the helminth parasites collected from the Red Sea fishes, Apharyngogyliauchen callyodontis Yamaguti, 1942 is reported for the first time parasitizing the middle and lower parts of the intestinal tract of Scarus psittacus (Common parrotfish) (Forsskål), collected from the northern Red Sea of Egypt. The encountered helminth was re-described morphologically and morphometrically based on the light microscope study. The current study demonstrated that some taxonomically important, previously unreported morphological and morphometric features, including the variation in; intestinal ceca length, and their posterior extension, testes position relative  to ventral sucker, cirrus-sac shape, pars prostatica shape and its extension inside cirrus, genital pore positions from median to nearly submedian, vitelline follicles distribution and its posterior extension, seminal receptacle shape, ovary shape and posterior extension of the uterus. The diagnostic morphological features were elucidated and discussed to provide correct identification of Apharyngogyliauchen species with very careful consideration to avoid overlapping with the closely related species.