In the present study the sub-lethal effect of copper on various haematological parameters of Clarias batrachus were studied. Copper (as copper sulphate) was used to prepare the stock solution from which different standard concentrations were prepared. A total of 16 specimens of Clarias batrachus (mean weight and length 100 gm and 18-20 cm, respectively). were used for this purpose. In exposed fishes various haematological changes were noticed. The RBC counts and haemoglobin percentage was decreased significantly from the normal values.