The aim of Present study was to investigate the effect of acute toxicity of Dichlorvos on total protein content in muscles of freshwater prawn Macrobrachium lamarrei lamarrei. Dichlorvos (2, 2-dichlorovinyl dimethyl phosphate), an organophosphate compound, which is commonly used as an agricultural insecticide. It is extremely toxic to non-target organisms like shrimps and other organisms of aquatic habitat. The effectof dichlorvos on total proteins in muscle was estimated in Macrobrachium lamarrei lamarrei. The prawns were randomly selected and stocked at the rate of 30 prawns per aquarium in two glass aquaria for the experimental runs. Prawns were exposed to 0.0075ppm dichlorvos for 96 hours. The total protein level was measured as (0.78mg/ml) at 0th day, (0.66mg/ml) at 15th day, (0.41mg/ml) at 30th day and (0.13mg/ml). The muscle proteins decreased consequently as compared to control group during the period of investigation.