Malathion is an organophosphorous insecticide widely used in agricultural and non agricultural purposes in India, creates a serious threat to the environment as well as target and non target organisms. The present investigation was undertaken to study the effect of malathion on some haematological parameters of Channa punctatus. Channa punctatus was treated with malathion and LC50 value for 96 hours was calculated following probit analysis methods. Channa punctatus was exposed to sublethal concentration of malathion (0.8 ppm). The study revealed a declining trend of RBC, Haemoglobin and increasing trend of WBC indicated toxic effect of malathion on Channa punctatus.