Abstract: The infestation of parasitic isopods in the fish Parastromateus niger was studied. Infested fish exhibited histopathological anomalies such as tissue reactions, primarily associated with the formation of granulomas consisted of macrophages and epitheleioid cells, which are occasionally surrounded by a thin rim of fibroblasts. The infestations such as lipofibrosis, hyperaemia, haemorhagic lesions and penetration of dactylus usually pressure atrophy often accompanied by the presence of parasites. Lesions had well developed granulomas that underlined in the muscle or overlying subcutaneous tissue, form these spread to underlying organs.