Juvenile orange-spotted grouper (Epinephelus coioides) were fed experimental diets with four levels of vitamin E (all-rac-α\-tocopherol) (0, 50, 500, and 5000 mg/kg diet) for 12 wk to investigate the effects of feeding these vitamin E-enriched diets on phagocytic, respiratory burst, and leukocyte proliferative activities. Fish fed the diet without vitamin E showed reduced growth, head-kidney leucocyte phagocytic activity, and proliferation, but no difference was detected in survival. When fish were fed 500 mg/kg dry weight (DW) vitamin E, enhanced phagocytic activity was found, which was significantly higher (p < 0.05) than those of fish fed the other diets. There were no effects of dietary vitamin E intake on respiratory burst activities of head-kidney leucocytes. Leucocyte proliferation was significantly higher in fish fed the diet with higher vitamin E levels (500 and 5000 mg/kg) than those fed the diet without vitamin E, when stimulated by Con-A, PHA-P, and LPS. Data showed that vitamin E (500 mg/kg DW) could efficiently stimulate grouper leucocyte phagocytic and proliferative activities, but not respiratory bursts.