An 8-week feeding experiment was conducted to evaluate the effects of dietary nucleotides (0, 0.5, 1, 1.5 and 2 g kg−1) on serum antioxidative biomarkers and lipid contents of rainbow trout fingerlings. The serum triglycerides and low-density lipoprotein (LDL)-C levels were significantly decreased in fish fed diets containing 1.5 and 2 g kg−1, whereas serum high-density lipoprotein (HDL)-C was higher in trout receiving diets with those levels of nucleotides. A significant decrease in thiobarbituric acid reactive substances concentration was observed in groups receiving 1.5 or 2 g kg−1 of dietary nucleotides in comparison with control group (−32% and −27%, respectively). A significant decrease was observed in catalase and serum glutathione peroxidase activity in trout fed 1.5 and 2 g kg−1 dietary nucleotides compare with other groups. There were no significant changes in serum superoxide dismutase activity among the experimental groups. In conclusion, these results suggest that dietary nucleotides may reduce lipid peroxidation by increasing the levels of antioxidant lipoprotein, HDL-C, and decreasing the LDL-C, the main substrate of lipid peroxidation.