Abstract: Forty eight crossbred male and female rabbits aged 12-14 weeks were used to study the effects of supplementing Coconut Shell Ash (CSA) on reproductive organ characteristics and serum sex hormone concentrations of growing rabbits. The rabbits were divided into 24 males and females, respectively. Each group was divided into four experimental treatments T1, T2, T3 and T4 of six animals and was further replicated three times with two animals per replicate in a Completely Randomized Design (CRD). The animals were fed a commercial grower rabbit ration which was supplemented with CSA at the rate of 0, 1, 2 and 3 g kg-1 b.wt., respectively. At the end of 12 weeks feeding, three rabbits were selected from each group, slaughtered and used to determine reproductive organ characteristics. Blood samples from the slaughtered animals were collected from the jugular vein and assayed for serum reproductive hormones concentrations. Data collected were subjected to analysis of variance. Testicular morphometry result showed that 1 to 2 g kg-1 b.wt. CSA supplementation could improve the weight of testis, size and epididymal weights indicating that up to 2 g kg-1 b.wt. CSA supplementation supported superior testicular development. This was associated with increasing serum testosterone concentration indicating probably a CSA enhancement of metabolic activity. One gram kg-1 b.wt. was the optimal CSA supplementation rate in female rabbits, since this led to improved weight of whole reproductive tract, weight of ovary, oviduct and uterus. This was equally associated with increased estrogen concentration, which increased with increasing CSA supplementation.