Two feeding trials were conducted to investigate the effects of several dietary additives on growth and feed utilization of juvenile flounder. In the first experiment, three replicate groups of juveniles (average weight 1.5 g) were fed diets with or without wasabi extract and chitosan for 7 weeks. Survival rate, weight gain, protein efficiency ratio, hepatosomatic index and condition factor were not affected by the different dietary additives (P>0.05). Feed efficiency of fish fed the wasabi extract diet was significantly higher than that of fish fed the control diet (P<0.05). Daily feed intake of fish fed the wasabi extract diet was significantly lower than that of fish fed the other diets (P<0.05). In the second experiment, three replicate groups of juveniles (average weight 1.4 g) were fed diets with or without Pophyra powder for 7 weeks. Survival rate and weight gain were not significantly affected by dietary Pophyra powder (P>0.05). Feed efficiency and protein efficiency ratio of fish fed the Pophyra diet were significantly lower than those of fish fed the control diet (P<0.05). The results of these experiments suggest that feed efficiency of juvenile flounder may be improved by dietary supplementation with wasabi extract.