This study was conducted to investigate the effect of dietary oxidized oil and ${alpha}$-tocopherol level on growth and body composition of juvenile flounder. To prepare oxidized diets, squid liver oil was oxidized by aeration at $25^{circ}C$ for 30 days. The six diets were prepared to contain 6% fresh or oxidized squid liver oil as the lipid sources in combination with three levels of ${alpha}$-tocopheryl acetate at 0, 80 and 800 mg/kg diet. Triplicate groups of fish ($3.9{pm}0.1$) were fed to apparent satiation twice a day for 8 weeks. Survival was not significantly different among treatments. Weight gain, feed efficiency, daily feed intake, protein efficiency ratio and condition factor of fish fed the fresh oil diets were significantly higher than those of fish fed the oxidized oil diets (P<0.05). The increase of the vitamin E level in diets did not result in any significant improvement on growth performance of fish fed both oil diets. The vitamin E content of the liver and dorsal muscle increased with increasing dietary vitamin E level at both oil diet groups. A decreasing trend in vitamin E content of the tissues was observed in fish fed the oxidized oil diets at the same dietary vitamin E level. Significantly higher moisture content and lower crude lipid content were observed in the whole body of fish fed the oxidized oil diets than fish fed the fresh oil diets (P<0.05). Dietary lipid source affected the fatty acid content of the whole body; higher contents of saturated and monoenoic fatty acids, and lower n-3 HUFA contents such as 20:5n-3 and 22:6n-3 were observed in fish fed the oxidized oil diets than those of fish fed fresh oil diets. The results of this study suggest that the dietary oxidized oil may impair the growth performance, and an increase in ${alpha}$-tocopheryl acetate supplementation have no beneficial effect on growth and feed efficiency of juvenile flounder.