Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day−1 and satiation (5.52% BW day−1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day−1 and satiation (4.12% BW day−1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day−1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day−1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day−1 whereas FE reached a plateau at 3.0% BW day−1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day−1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day−1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day−1 for 5.0 g, and it could be >3.0 but <3.47% BW day−1 for 20 g size of juvenile olive flounder at the optimum rearing temperature.