Heavy metals, nowadays are the major environmental problems which deteriorate the natural phenomenon of all the living beings of the ecosystem. The present investigation was carried out in two freshwater fishes, Cyprinus carpio and Oreochromis niloticus exposed to Lead acetate and Nickel chloride to determine the lethal concentration (LC50) for 96 hour. The 96h LC 50 for both the species was computed as 14.35 mg/L (O.niloticus) and 16.75 mg/L (C.carpio). The same fishes were treated with sub-lethal concentrations for determining the hematological parameters. All the variations in parameters were dose dependent and were in parenthesis. The experiment was carried out for four weeks and observed that erythrocytes count, hemoglobin and the hematocrit value increased gradually with exposure time while the leukocytes count decreased. Serum protein and serum glucose were found to be affected significantly. Lead acetate seems to be more effective than the nickel chloride.