Growth performance, carcass composition, and immunophysiological indices in juvenile great sturgeon (Huso huso) fed on commercial prebiotic Immunoster (IS) were investigated. After a four-week acclimatization period, 270 great sturgeon juveniles weighing 95.68 ± 10.05 g were randomly distributed into 9 fiberglass tanks in three replicates and kept at a density of 30 fish per tank for a period of 8 weeks at water temperature 20.55 ± 5.11ºC and dissolved oxygen 6.73 ± 0.35 mg L-1. IS was added at two levels of 1% and 3% to the basal diet in place of cellulose. At the end of the trial, blood sampling and carcass analysis were conducted. Weight, length, body weight increase (BWI), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER) and condition factor (CF) were significantly affected by IS 3% compared with IS 1% and the control (P<0.05). There was significant difference (P<0.05) in crude protein of carcass between the experimental groups. Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) showed significantly higher levels in experimental treatments compared with the control (P<0.05). Immunoglobulin M (IgM) level and lysozyme activity in IS 1% group were higher than the control group. It can be concluded that IS can enhance growth performance and improve some immunophysiological indices of great sturgeon.