This experiment was conducted to evaluate the Impact of supplementing diet with Moringa oleifera leaves (MOL) and vitamin C on growth performance, blood constituents, antioxidant indices and hormone profiles of Japanese quails under subtropical climatic conditions. A total 180 unsexed Japanese quails chicks, 7day old were randomly distributed into 6 groups housed with 3 replicate, 10 chicks/ each. In the 1st group (control), chicks were fed on a basal diet, while those in the 2nd (T1), 3rd (T2), 4th (T3), 5th (T4) and 6th (T5) groups were fed on the same basal diet supplemented with 3g MOL/kg diet, 6g MOL/kg diet, 200ppm Vit. C, 3g MOL/kg diet + 200ppm Vit. C, and 6g MOL/kg diet + 200ppm Vit. C respectively. Average maximum room temp ͦ C during the day between 40-45 °C and 50% relative humidity were recorded during the experimental period until 6 weeks age. The obtained results showed that the chicks supplemented with 6g MOL/kg diet + Vit. C 200ppm had significantly greater body weight, body weight gain, Feed consumption and percentages of dressing and internal organs and improved feed conversion ratio, followed by (T2), (T4) then (T3) and (T1) compared with control group. The hematological traits, immunity parameters, antioxidant indices for chicks in treated groups were significantly (P<0.01) improved compared with control group. Serum proteins, albumin, globulin, high density lipoproteins (HDL) and thyroid hormones were significantly improved, while total serum lipids, cholesterol, glucose concentration, low density lipoproteins (LDL), liver enzymes, creatinine and urea were significantly (P<0.01) decreased compared with control group. However, no significant effects were detected on white blood cells due to the addition of different treatments compared to the control. The bacterial count in chick intestine were remarkably decreased due to addition MOL and Vit.C at different levels compared to the control. It can be concluded that MOL supplementation in Japanese quail diets is a good natural source and can be used as a safe alternative to synthetic Vit.C under subtropical climatic conditions