Fish are an important source of protein with low cholesterol, unfortunately fish are liable to many   parasites, which have an important effect on fish aquatics, besides their zoonotic importance. Our main objective in this study is to evaluate parasitic infection in African catfish and Nile tilapia and their histopathological effects on infected fish. Two hundred fish samples, 150 catfish and 50 tilapias were collected from the River Nile of Damietta governate, Badr city market, Manzalla city market and Menoufia governate market from January 2022 to February 2024. The identified parasites in catfish were Encysted metacercaria with prevalence rate (20%), which affected skin and muscles. Microscopically, Encysted metacercaria appeared as parasitic cysts surrounded by fibrous connective tissue capsule, Polyonchobothrium sp. with prevalence rate (20%), affected the intestine. Microscopically, intestine showed desquamation of mucosa and goblet cell hyperplasia and Dactylogyrus sp. with prevalence rate (10.5%), caused marbling appearance of gills. Microscopically, gills showed hyperplasia and telangiectasis. The identified parasites in tilapia were Encysted metacercaria with prevalence rate (22%), caused many hemorrhagic patches in liver. Microscopically, it showed hydropic degeneration and fatty change, Chilodonella sp. with prevalence rate (6%), caused necrosis of gills. Microscopically the gills showed desquamation of epithelium, Gyrodactylus sp. with prevalence rate (4%), caused dark discoloration of the skin. Microscopically, the skin revealed many alarm cells and abundant melanomacrophages. and Cymothoid Isopods with prevalence rate (2.8%), caused hemorrhage in gills. Microscopically, the gills showed hemorrhage and loss of gill filaments.