Profenofos is commonly used pest control in the agricultural fields surrounding freshwater reservoirs. This study was conducted to determine the acute toxicity of organophosphate pesticide and its effects on some haematological parameters of fresh water teleost fish Notopterus notopterus. The experimental groups showed decreased RBC, and Hb at 24 and 96 hrs exposures, and WBC value were found decreased at 24 hrs and increased at 96 as compared to control groups respectively. The results of examinations of blood profile indicate marked nuerotoxic effect of profenofos in fishes. The changes in values of both erythrocyte and luekocyte profile after exposure to profenofos based preparation may be referred to disruption of haematopoiesis as well as to a decrease on non-specific immunity of the fish.