This study aimed to evaluate the effect of, replacing corn grains in concentrate feed mixture (CFM) with mango seeds (MS) in Damascus goat buck's diets, on productive and reproductive characteristics at prepubertal stage (weaning-prepuberty). Corn grains in CFM were replaced with mango seeds at levels of 0% MS (G1, control), 15% (G2) and 30% (G3). Results revealed that G3 showed the highest (P<0.05) LBW and average daily gain (ADG). Feed conversion ratio, all nutrients digestibility, feeding values, and economic feed efficiency were improved (P<0.05) in G2 and G3 compared with G1. Animals in G2 and G3 showed earlier (P<0.05) ages to produce the 1 st ejaculation than control. Testosterone concentration one-month prepuberty increased (P<0.05) in G2 compared with G1 and G3. Testicular measurements and scrotal circumference in G2 as well as only testicular length in G3 increased (P<0.05) in comparing with G1. Mediastinum width increased in G2, decreased in G3 compared with G1 (P<0.05). Tunica albuginea was thicker (P<0.05) in G2 and G3 than in G1. Scrotal septum was wider (P<0.05) in G3 than in G2. Prostate and vascular gland were longer (P<0.05) and wider in G2 and G3 than in G1. This study concluded that replacement of corn grains with mango seeds at level of 30% in diets of Damascus goat bucks has a positive effect on productive performance. The replacement at a level of 15% MS improved reproductive characterization of bucks raised for semen production for breeding programs.