The study was aimed to investigate the sub lethal effect of insecticide, Chandika 505 mixture of chlorpyrifos 50% and cypermethrin 5% EC to zebra fish (Danio rerio). The acute toxicity LC50 of insecticide was determined at 96 hrs and the value is 22.7 ppb and sub lethal concentration is 7.56 µg. Behavioral changes were also observed when fish were subjected to different concentrations of the insecticide. The results of the present study indicate increase in the total lipids, free fatty acids and cholesterol in gills, viscera and body of zebra fish. Hence it can be concluded from the results that measures should be taken for the usage of insecticides in order to protect the aquatic environment because combined toxic effects of pesticides are important in ecotoxicology since mixtures shave a greater effect than the individual pesticides. Keywords: Zebra Fish, LC50, mixtures, Chlorpyrifos, Cypermethrin.