The fish, Oreochromis mossambicus was treated with two different (10% and 30%) sublethal concentrations of pesticide fipronil 5% SC (LC50 for 96-hour ppm - 0.006 ppm) to study on the effect in the biochemical components for a long-term exposure. In this study, biochemical compositions (carbohydrates, protein and lipids) in various tissues such as gill, intestine, kidney, liver and muscle were decreased with increase in exposure periods. Maximum decrease over control in the biochemical composition was noted in 30% sublethal concentration of pesticide fipronil on 30 days of exposure.