Copper sulfate is one of the most important pollutant in aquaculture systems. The aim of the present study was of the histopathological changes of some organs of common carp. copper sulphate can be considered as a toxic agent for fish.The effect of copper sulphate at 0. 0 1 mg/L as a constant bath was studied on Common carp (Cyprinus carpio) weighing about 100g. at 19±1°C for one month. Tissue samples of liver, gill, gonads and skin were obtained, fixed in 10% formalin, processed using routine histotechnique method and the 5 micron sections were stained with hematoxylin and eosin. Focal necrosis, vacuolation, picnosis, karyorrhexis of neuclear hepatocytes, infiltration of lymphocytes into connective tissue of liver and hyperemia were observed in liver samples. In the gonads tissue, inflam matory cells infiltrations and hemosiderin pigment were observed. There were, edema, hyperplasia, fusion of branchial cells, increased number of moucus and chloride cells observable in the gill sections. The main renal lesions were necrosis in proximal ducts. Accordingly, we can conclude that some tissue lesions occure in different organs of common carp after chronic exposure to copper sulfate (0. 0 1 mg/L).