This study was performed to determine effects of dietary inclusion of various concentrations and sources of sea tangle Laminaria japonica on growth, body composition and plasma chemistry of juvenile black porgy Acanthopagrus schlegeli. Juvenile fish (N=810; average mass=8.9 g) were distributed among twenty-seven 200 L flow-through tanks (30 fish per tank). Nine experimental diets were prepared: control (Con) without additives; sea tangle powder at 0.1%, 0.5%, 1%, 2%, 3% and 5%, (P-0.1, P-0.5, P-1, P-3 and P-5 diets, respectively); and fresh sea tangle (F-1); and 1% sea tangle extract (E-1). Each powdered additive was substituted for an eqaul amount of wheat flour, and the extract was substituted for an equal amount of water in the respective experiemtnal diets. Each diet was fed to triplicate groups of fish. Weight gain and feed conversion ratio were not affected by the experimental diets. Feed consumption by fish fed the P-1 diet was higher than that of fish fed the P-3 and P-5 diets. Moisture, crude protein, crude lipid, whole-body ash content (excluding the liver), liver moisture, and crude protein and lipid contents of fish were not affected by the experimental diets. None of the fish plasma criteria were affected by the experimental diets, with the exception of plasma glucose. In conclusion, dietary inclusion of various concentrations and sources of sea tangle did not significantly affect the growth, feed efficiency, body composition or plasma chemistry of juvenile black porgy.