Sturgeons are an economically important freshwater aquacultural fish in China and elsewhere. Research was conducted to study the magnesium requirement of juvenile hybrid sturgeon (Acipenser schrenckii♀ × Acipenser baerii♂) based on mineral composition, proximate chemical analysis, antioxidant enzyme levels, and growth metrics. Different levels of magnesium supplements (43.2, 157.3, 326.5, 549.6, 743.9, 938.4, and 1118.2 mg kg⁻¹) were fed to juvenile sturgeon for 8 weeks. Five hundred twenty-five juvenile hybrid sturgeons (an average initial body weight of 7.65 g) were randomly divided into 7 groups with 3 replicates each (25 fish per replicate, tanks of 100×50×50 cm, dissolved oxygen ≥ 5.0 mg L⁻¹, 12 light:12 dark) and fed 4 times per day with the experimental diets containing 40.78% crude protein and 10.03% crude fat. The body tissues and blood of fish were then sampled and analyzed. Growth performance was not significantly different between treatments (P>0.05). The optimal dietary magnesium requirement for hybrid sturgeon was estimated to be 355.16, 573.6, or 584.6 mg kg⁻¹ dietary magnesium based on whole-body Mg retention, the whole-body or vertebrae magnesium content versus dietary magnesium levels. The whole-body calcium to phosphorus ratio of the 43.2 and 326.5 mg kg⁻¹ groups was significantly higher than that of the 938.4 mg kg⁻¹ group (P< 0.05). A dietary magnesium concentration of 350–700 mg kg⁻¹ improved the antioxidant capacity by decreasing the serum malondialdehyde and enhancing serum superoxide dismutase, glutathione peroxidase, and catalase activities.