The purpose of this study was to investigate the effect of the dietary mulberry (Morus Nigra) fruits juice as natural antioxidative additive given under high ambient temperature on their performance and some blood parameters of Muscovy ducks. The experiment was conducted for 8 weeks, using 100 Muscovy ducks, aged 21 days. The first group was fed the basal diets, while the diets of groups 2, 3 and 4 also thoroughly mixed with black mulberry fruits juice at a rate of 1, 2 and 4 %, respectively. Results showed that the average biweekly body weight gain, final weight, and feed conversion ratio were improved in mulberry juice groups compared to control group. The biweekly feed consumption was increased significantly with mulberry juice groups than control group. There were an improvement in the immune response of treated ducks, in terms of significant increases in WBCs count, Heterophils, Lymphocytes and serum globulin level in the experimental groups compared to control group. Blood glucose, HDL and GSH concentrations increased significantly in black mulberry juice groups compared with control group. But, creatinine, total lipid, cholesterol, triglyceride, LDL and MDA concentrations decreased in the experimental groups. Results indicated that slaughter weight, carcass and dressing percentage were increased significantly by mulberry juice groups, to reach (102.3, 105.2 and 109.2%); (102.9, 103.7 and 104.4%) and (102.9, 103.3 and 103.8%) of control, respectively. Liver, bursa and abdominal fat percentage were reduced significantly with the mulberry juice groups to reach (95.4, 99.0 and 92.4%), (95.4, 97.0 and 90.1%) and (97.1, 97.1 and 109.0%) of control group, respectively. It can be concluded that dietary black mulberry juice addition to high ambient temperature Muscovy ducks can reduce physiological strain, cholesterol level and oxidative effect.