This study aimed to evaluate the effects of different levels of dietary Quillaja saponin on the growth performence, digestive enzymes, water quality, and immune response of common carp in biofloc system. The fish (8.06 ± 0.59 g) were fed diets containing 0 (BC), 15 (BS1), 30 (BS2), and 60 (BS3) mg/kg saponin powder for 60 days. The growth performance and protease were significantly higher in the fish fed with a saponin diet in biofloc environment (P< 0.05) while no significant effects on Food conversion ratio and lipase enzyme (P> 0.05). Total ammonia nitrogen (TAN) concentration was significantly lower in the saponin-fed groups than in the control (P< 0.05). The highest serum total immunoglobulin levels, lysozyme, and complement (ACH50) activities were observed in the diet containing saponin powder in biofloc system (P< 0.05). The present results show that Quilaja saponin can be used as a potential feed additive for farmed fish in biofloc system.