Physiological functions of animals get disturbed on exposure to pollution stress. The better understanding of this mechanism can help us to predict the harmful effects of various chemicals on environment. This study estimates the chronic effect of this pesticide on biochemical composition of protein. The sublethal concentration of Triazophos treated with Oreochromis mossambicus protein level at different time interval and observed that in the liver, muscle and intestine protein level showed declined trend. The changes in the level of protein contents in muscle, liver and intestine of the fish O .mossambicus. The decrease in protein content of Triazophos in toxicated fish in the present study also indicates the physiological adaptability of the fish to compensate for pesticide stress.