In the present study the effect of L-carnitine supplementation on biochemical parameters (total protein, total lipid, glucose, cholesterol, triglyceride, globulin, albumin and free fatty acid) and antioxidant activity (superoxidase dismutase (SOD) and glutathione peroxidase (GPX)) in yellow fin seabream was investigated. A number of 240 fish with mean weight of 3.23 ± 0.46 g were randomly assigned into four groups (three replicates, 20 fish per tank) in 60 L-plastic tanks and fed with four experimental diets prepared by adding carnitine at the concentrations of 0, 400, 800, and 1200 mg kg-1 diet (referred as C0, C400, C 800 and C1200, respectively). After nine weeks of the feeding trial, a significant increase in free fatty acids, globulin, albumin, total protein, SOD and GPX and a significant decrease in cholesterol, triglyceride and total lipid were observed, in the fish fed with C800 diet compared to those fed with other diets. The diet containing 800 mg kg-1 dietary L- carnitine may have a marked effect on biochemical indices and antioxidant activity of yellow fin seabream.