This experiment aimed to determine the effects of supplemental sumac (Rhus coriaria L.) fruit powder (0, 1, 3, 5 and 10 g kg-1) on growth performance, intestinal histological alterations, survival, serum biochemistry, and antioxidant status of rainbow trout (Oncorhynchus mykiss, Walbaum). The feeding trials were replicated in three tanks each for a total of 15 tanks. The study was conducted for eight weeks. At the beginning of the experiment, 30 rainbow trout (initial weight: 35.67 +/- 0.88 g) were randomly stocked into each tank. At the end of the experiment, growth performance improved in the fish fed sumac fruit powder; however, other than the final body weight, the differences were not significant (P 0.05). The final body weight increased for treatments 1, 3, and 5 g kg-1 (P = 0.18). Intestinal morphology was enhanced in the experimental groups (P < 0.05). No differences were observed in serum biochemistry with sumac powder supplementation. The effect of sumac powder on superoxide dismutase (SOD), catalase (CAT) activity, and malondialdehyde (MDA) levels were also investigated for the overall antioxidant status. SOD activity in muscle was higher in fish fed diets containing various doses of sumac powder than in the controls (P < 0.05). In conclusion, the supplementation administration of sumac powder showed a positive effect on the growth performance, intestinal tissue morphology, and antioxidant enzyme stimulation in rainbow trout.