Effects of different levels of ascorbic acid consisting of 0, 100, 200, 400, 800 and 1600 mg/kg feed were examined on some immune variables of juvenile great sturgeon (Huso huso) weighing 38 g at water temperature 20°C for 16 weeks. Significant difference were observed in level of lysozyme in fish treated 400 and 1600 mg compared with control group 8 week post-treatment (p<0.05). Also levels of lysozyme in fish treated ascorbic acid were insignificantly higher than control group (p>0.05) 16 weeks post-treatment. Maximum level of leucocytes population was seen in fish treated 100 and 200 mg ascorbic acid 8 and 16 weeks post-treatment, respectively. Maximum antibody titer was observed in fish fed diet 200mg ascorbic acid (p>0.05). It was no found any mortality in treatment groups after challenge with Aeromonas hydrophola compared with 29.9% mortality in control group (p<0.05). The obtained results showed that vitamin C has beneficial effects on some immunological variables of juvenile great sturgeon making fish become more resistance to infectious diseases, especially during early life stage at which fish are more sensitive to the pathogenic microorganisms and unfavorable environmental conditions. Therefore, using vitamin C in early life stage of great sturgeon can cause an enhancing in immune responses of fish resulting in resistance to infectious and uninfectious diseases.