This study was conducted to evaluate the effects of extruded pellet (EP) diets, as compared to a raw fish moist pellet (MP) diet for olive flounder, Paralichthys olivaceus, grown in commercial-scale aquaculture for 1 year. Four diets with duplication per diet were formulated for this experiment: two experimental EP diets (EP1 and EP2), one commercial EP diet (CEP), and a raw fish MP diet (MP). The MP diet consisted of 80% frozen horse mackerel and 20% commercial binder meal. Fish weighing $30.1{pm}0.1 g$ ($mean{pm}SD$) were distributed randomly to each aquarium as a group of 2,600 fish. Weight gain (WG) and feed efficiency ratio (FER) of fish fed EP2 and MP were higher (P<0.05) than those of fish fed CEP, while those of fish fed EP1 did not differ (P>0.05) from those fed EP2 and MP. However, fish fed the MP diet had a higher survival rate than fish fed the other diets. Fish fed EP2 had higher serum, phospholipids and total protein levels, and lower levels of serum glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), and total cholesterol than fish fed MP (P<0.05). Dorsal muscle and liver proteins and lipid of fish fed EP1 were higher (P<0.05) than those of fish fed CEP, while those of fish fed EP1 and MP did not differ from those of fish fed EP2 (P>0.05). These results strongly suggest that EP1 could be developed to replace MP for grow-out stage production of olive flounder without adverse effects on growth performance.