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The effect of cypermethrin pesticide on juvenile rohu (Labeo rohita) was determined in captive condition. Live and healthy rohu (average initial weight 21g) were exposed to five concentrations of Cypermethrin 0.63, 0.13, 0.025, 0.005, 0.001 ppm and one control group (no pesticide) with two replications for each treatment. The mean temperature and pH in the experimental tanks were 27.53±0.41ºC and 7.22±0.013 ppt, respectively. The highest growth recorded in control tank was 0.2g per week, where as nosignificant growths were found in 0.001 ppm and 0.005 ppm concentration. Rohu reared in the 0.13 ppm had the lowest growth. The median lethal concentration values were found at 0.025, 0.005 and 0.001 ppm for 9th, 17th and 20th day, respectively. Behavioral patterns were observed in both lethal 0.63, 0.13 ppm and sub lethal concentration 0.025 ppm. L. rohita in toxic media exhibited erratic and darting movements with imbalanced swimming activity, which might be due to the malfunctioning of neurotransmitters, followed by hyper and hypo opercula activity, loss of equilibrium and mucus secretion all over the body were observed