Blood biochemical parameters are important factors that can show the changes in health offering critical feedback on physiological condition of fish. In the present study, we examined a comparative study on the blood biochemical parameters in mature male and female goldfish, Carassius auratus. Plasma samples of 72 male and female goldfish that have been kept at 24°C for 30 days were analyzed and their biochemical parameters levels were determined. There were significant differences in all measured parameters between genders so that, maximum concentrations of the glucose (73.45±0.68 mg/dl) and calcium (8.32±0.05 mg/dl) were found in female fish, while the highest levels of the total protein (3.14±0.01 g/dl), cholesterol (281.65±3.19 mg/dl) and triglyceride (428.31±1.17 mg/dl) were measured in males. Based on the results, the plasma biochemical parameters changes vary considerably between male and female goldfish