The growing demand for natural-based chemicals in broiler nutrition has necessitated the need to develop sustainable and novel natural products to replace the environmentally unfriendly synthetic chemicals. This study aimed to evaluate the chemical composition and antioxidant potentiality activity of aqueous mango leaf extract (AMLE) and to know whether the extract can be used as an additive in drinking water to enhance the immunity of broiler chicks by evaluating growth performance, carcass characteristics and plasma biochemical indicators. A number of 216 unsexed one-day-old Ross 303 broiler chicks were randomly divided into three groups with six replicates of 12 chicks each. Birds in the first group drank water with no addition (control), while those in the second and the third group drank water supplemented with 10 and 20 mL AMLE per liter, respectively. The results showed that the extract had high antioxidant activity. GC-MS analysis revealed ten components in AMLE. The major compounds identified were 3-(Prop-2-enoyloxy) dodecane (27.93%),Hexadecanoic acid, methyl ester (13.68%), 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl (10.41%), Docosanoic acid, methyl ester (9.53%), n-Hexadecanoic acid (7.84%). In addition, the results revealed that birds of the second and third groups showed significantly improved carcass weight, dressing percentage, hematological, biochemical, and antioxidants indicators compared with the control group. These results encourage the use of AMLE to stimulate growth and to strengthen the immune system of broiler chickens.