This study's gaol is to ascertain the impact of diazinon about the condition of common carp, a significant fish species used for food in aquaculture ( Cyprinus carpio). The LC50 of diazinon after 96 h was 9.5 mg/L in C. carpio (78.8 ± 5 g in weight). The fish were divided into six tanks as two treatments in order to ascertain the long-term effects of diazinon (three tanks per treatment). They were subjected to diazinon (2.37 mg/L; 25% LC50-96 h concentration) and 0 (control) for 4 days, 14 days, and 28 days before blood biochemical assays were performed on samples taken. Dry- chemistry analyzer was used to determination the Liver Function enzyme, also SOD and CAT was estimated by use spectrophotometer. At day four and day fourteen, the plasma SOD activity of the diazinon-exposed fish did not significantly decrease in comparison to the control group; however, after day twenty-eight, the plasma SOD activity of the diazinon-exposed fish significantly increased in comparison to the control group. Diazinon exposure and control report a significant increase in serum CAT activity. Diazinon exposure increased significantly in serum ALT, AST and ALP activity compared to the control group.