Abstract: The present investigation was carried out to understand the impact of curacron on Serum aminotransferases activity (ALT and AST) of fresh water fish Cyprinus carpio. Curacron is an organophosphate pesticide and is widely used by the farmers to protect their crops. So every year huge volume of Curacron enters to aquatic ecosystems. The objective of this study was to determine the effect of curcuron pesticides and its influence of serum biomarker enzyme (ALT and AST). LC50 of Curacron for Cyprinus carpio has been calculated by the log-dose/probit regression line method and recorded as 0.38 ppm at 96 h. Three sub-lethal concentrations (0.1, 0.01 mL and 0.001 ml L-1) were selected to expose the fish for 1, 7, 14 and 21 days. Changes in enzyme activity were observed with all concentrations and exposure period. ALT and AST concentrations were significantly higher in the experimental group, compared with the control group. The above results of blood plasma profile indicate a marked cytotoxic and hepatotoxic effect of curacron in Cyprinus carpio.