Nurocombi is used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. The present research purposed to evaluate the effect of sub lethal concentration of nurocombi in hematological parameters of the fresh water crab, Paratelphusa jacquemontii after 0,7,14,21 and 28 days. Total counts of hemocytes showed decreasing trend as the duration of exposure in each concentration of nurocombi increased. Differential hemocytes count showed increasing trend as the duration of exposure in each concentration of nurocombi increased in Agranulocyte and Eosinophilic granulocyte. Differential hemocytes count showed decreasing trend as the duration of exposure in each concentration of nurocombi increased in Hyalinocyte and Basophilic granulocyte. It is concluded that hematological changes provide reliable and discriminatory data to augment pesticide pollution and therefore, long-term monitoring is necessary to assess the eco-health of the mangrove system.