An experiment was conducted during 7 months to test. the effect of triploidy on growth, sexual maturation, carcass and chemical analysis of O. niloticus. Triploid O. niloticus had heavier and longer bodies than diploids from 3 to 7 months of age, and the differences were not significant only for body length. This trend was also observed for condition factor,. daily gain and specific growth rate. Feed conversion ratios were better for triploids at some studied ages. In triploid of both sexes, the values of Gonado-somatic indices (GSI) were smaller than diploids with significant differences between the two ploidy groups. But Hepato-somatic indices, (HSI) of triploid O. niloticus males were larger than that of diploid with significant differences between the two groups. However HSI of triploid females were smaller than that of diploid females but the differences were insignificant. Carcass traits of O. niloticus had the higher percentages of dressing, viscera, by-products and lower percentages of flesh as compared with that obtained from the diploid.