The effect of dietary β-Ο-glucan, vitamin E, and β-carotene supplements in juvenile brown shrimp, Farfantepenaeus californiensis, inoculated with white spot syndrome virus (WSSV) was evaluated. Groups of 30 organisms (weighing 1 ± 0.5 g) were cultured in 60 L fiberglass tanks and fed daily with β-1.3-glucan (0.1%), vitamin E (0.01%), and β-carotene (0.01%) for 23 days; the specimens were then inoculated with WSSV. The antioxidant activity of the enzymes superoxide dismutase (SOD) and catalase (CAT) were determined in the hepatopancreas and muscle at 0, 1, 6, 12, 24, and 48 h after inoculation. Shrimp fed with β-1.3-glucan, vitamin E, and β-carotene significantly increased SOD activity in the hepatopancreas and muscle at 12 and 24 h post-infection, respectively. Shrimp fed with vitamin E and β-1.3-glucan registered an increment in SOD activity from 12 to 48 h post-infection. Shrimp fed with β-carotene increased SOD activity before infection with WSSV, and shrimp fed with β-1.3-glucan and vitamin E increased CAT activity, also before infection. The CAT activity response in shrimp muscle increased with respect to the control group for all treatments tested from 1 to 6 h after inoculation with WSSV. The highest antioxidant response was registered in shrimp fed with vitamin E. Juvenile shrimp fed with vitamin E and later inoculated with WSSV registered 100% mortality at 72 h, but shrimp fed with β-Ο-glucan and β-carotene showed greater resistance to WSSV, with mortality at 144 h post-infection. This study demonstrated the capacity of juvenile Farfantepenaeus californiensis fed β-Ο-glucan, vitamin E, or β-carotene to increase the antioxidant response before and after viral infection.