A study was conducted to investigate effects and interactions of magnesium (Mg) and vitamin E (VE) on growth performance, body composition, hepatic antioxidant capacity and serum biochemistry parameters of juvenile Japanese seabass Lateolabrax japonicus under oxidative stress condition. Fish (initial average body weight of 6.10 AE 0.20 g) were fed 9 oxidized oil diets supplemented with 3 grade levels of Mg (0, 520 and 1570 mg kg À1 diet) and VE (0, 60 and 200 mg kg À1 diet) for 8 weeks in freshwater. The results showed that diets supplemented 520 mg kg À1 Mg and/or 60 mg kg À1 VE had highest growth and muscle lipid content. There were highest total superoxide dismutase, catalase, glutathione peroxidase activities and lowest malondialdehyde content in liver of fish fed diets supplemented 520 mg kg À1 Mg and/or 60 mg kg À1 VE. Contrary to Mg concentrations, Ca concentrations and Ca/Mg ratio in whole body were inversely related to dietary Mg levels. However, combined deficiency or excess of dietary Mg and VE led to the decrease of hepatic antioxidant capacity, body lipid deposition and growth of Japanese seabass under oxidative stress condition.