Abstract:Cadmium is a heavy metal widely used in industrial processes, has been recognized to be a highly toxic and dangerous environmental pollutant. These excess amounts in addition to naturally occurring levels gradually build up to toxic levels causing damages to the biota of the aquatic ecosystem. The fresh water field crab, Paratelphusa hydrodromous is an important human food source in parts of South India. Evaluation of the toxic effect of cadmium on the experimental crab for the LC 50 value was carried out. Effect of cadmium on the oxidative damage and biomarkers antioxidant enzymes in the hepatopancreas was observed. Quantitative study of antioxidant enzymes GSH, GPx, ACP and ALP were undertaken, result and discussed in detail.