Juvenile abalone, Haliotis discus hannai Ino (initial mean body weight: 0.56 ± 0.01 g, shell length: 15.74 ± 0.13 mm) were fed six diets with graded levels of pyridoxine (PN) (0.40, 12.5, 22.7, 43.5, 87.8, and 172.2 mg/kg diet). Each diet was fed to three replicate groups of juvenile abalone for 16 wk. Dietary PN significantly (P < 0.05) affected abalone growth, tissue concentrations of PN and pyridoxal 5′-phosphate (PLP), and the activities of asparatate aminotransferase (AST) and alanine aminotransferase (ALT). The responses of all these parameters to dietary pyridoxine levels fitted the broken-line model. Broken-line regression analyses showed that the breakpoints were 23 on the basis of growth data, 32–38 on tissue concentrations of PN and PLP, 20–21 on the activities of visceral AST and ALT, and 39–40 on the activities of muscle AST and ALT. Hence, the requirement of H. discus hannai for dietary pyridoxine should be 23 mg/kg diet for maximum growth, and about 40 mg/kg diet for the saturation of tissue PN and PLP, or tissue aminotransferase activities.