The discharge of improvident and inconsiderable level of organophosphorous pesticide, especially cypermethrin into aquatic bodies have caused ecological problems to all classes of aquatic organisms including fish. The study was made in assessing the toxic effects of cypermithrin on behavioral and mortality parameters of mirror carp, Cyprinus carpio.The observed percentage mortality of fresh water fish Cyprinus carpio when exposed to the 10% emulsifiable concentration (E.C.) cypermethrin for time periods 24, 48, 72 and 96 h in static system toxicity is in the range of 0.26ppm, 0.23 ppm, 0.16 ppm, 0.14 ppm respectively. In the present study, the experimental fish exhibited different toxicity level for various time exposures. The mortality of the fish at different concentration of cypermethrin was determined at 24, 48, 72 and 96 h exposure. With the increase period of exposure (96 h), the fish showed mortality at less concentration and with decrease of duration of exposure the fish exhibited mortality at higher concentration. Several behavioral changes were observed when exposed to sublethal concentration of pesticides such as loss of schooling behavior, swimming near the water surface, hyper activity, erratic movements, seizures, loss of buoyancy, elevated cough, restlessness before death, darting movements and hitting against the walls of test tanks were noticed in all the species tested. A film of mucus was also observed all over the body and also on the gills. The study showed that use of cypermethrin is threat for the mirror carp and hence should be legitimated to use in agriculture.