Static bioassays were carried out to find the LC50 96 hr value of Cypermethrin to Cyprinus carpio and it was found to be 2.0 ppm. Then a group of fishes were recorded in a selected reared sub lethal concentration of the pesticide (0.2 ppm) for 4 weeks. From the control and treated fishes, serum and tissues like gill, liver, kidney and muscle were selected and used for the estimation of antioxidant parameters. There was an overall reduction of various antioxidant enzymes such as SOD, GSH, GR and GPX and an elevation of TBARS level. These results were indicative of occurrence of LPO with resultant ROS causing oxidative stress in the fishes by the pesticide.