Abstract: Tilapias are yet to reach their full aquaculture potential because of the problem of prolific breeding which usually results in overpopulation thus leading to stunted growth. The potential use of Azadirachta indica leafs as an antifertility substance in controlling prolific breeding in Oreochromis niloticus was investigated. Crude extract of Azadirachta indica leaves were added to a basal diet (35% crude protein) at 0.0, 0.5. 1.0, 2.0, 4.0 and 8.0 g kg-1 diet, respectively (D1, D2, D3, D4, D5 and D6) and fed to 180 Oreochromis niloticus (90 males and 90 females) Mean±SD weight of 29.30±2.02-31.79±3.11 g twice daily (0900-0930, 1700-1730) at 3% of their body weight for 56 days to evaluate the effects on growth and reproduction. There was variation (p<0.05) in growth parameters with fish fed 1.0 g kg-1 diet showing best Mean±SD weight gain of 19.68±3.22 g. A total of 63-89 hatchlings were counted in the control tank in the 3rd week and 35-51 hatchlings from fish fed with 0.5 g kg-1 diet in the 5th week, there was no breeding in the groups; D3, D4, D5 and D6 during the course of this study. This study infers that Azadirachta indica leafs extract could be used in controlling prolific breeding in Oreochromis niloticus for efficient and sustainable development of tilapia farming.