Abstract: The protein level of blood, liver and muscle in Anabas testudineus exposed to sublethal and median lethal concentrations of pesticide, dimethoate showed gradual decrease, which was statistically significant. The acid phosphatase activity in the blood, liver and muscle of Anabas testudineus was found to increase on exposure to sublethal and median lethal concentrations of dimethoate. The changes were concentration and duration dependent. Rise in the activities of acid phosphatase along with a reduction in protein content in the different tissues suggests enhanced protein catabolism to meet energy demands.