Abstract: A feeding trial was conducted to evaluate the effects of a commercial prebiotic, immunogen on growth performance and survival of the kutum Rutilus frisii kutum fingerlings. The fingerlings were adopted for 2 weeks and then reared as triplicate groups in 250-l tanks (n = 50 per tank with average initial weights of 499.1±5 mg). Four incremental levels (0.5, 1.0, 1.5 and 2.5 g kg^-1 prebiotic diet) of a commercial prebiotic, immunogen (Provided by Soroush radian Co., Tehran, Iran) were added to the basal diet A (control) to prepare diets B, C, D and E as the treatments. The fish fed on the experimental diets ad libitum thrice a day for 8 weeks. Weight gain and specific growth rates showed significantly differences among the groups fed different immunogen levels. Feed conversion ratio showed a decrease with increasing immunogen level in diet. Both feed and protein efficiency ratios enhanced significantly with the highest prebiotic level of 2.5 g kg^-1 diet (p<0.05). Feed Intake (FI) and Protein Intake (PI) didn’t significantly affect by the prebiotic immunogen level (p>0.05). The lowest mean of total bacterial counts was observed in the fish fed a dietary immunogen level of 2.5 g kg^-1 diet (p<0.05). The present study shows that a dietary immunogen supplementation of 1.5 g kg^-1 is capable to improve the feed efficacy and growth performance of R. frisii kutum fingerlings.