The present study throw lights on the effect of feeding of steroidal compound (17 α MT) on O. niloticus fry representing the following parameters (percentage of sex reversed fish, fish growth, level of total testosterone in plasma, body composition parameters, gonado-somatic index and gonadal histology). Fish were cultured under similar feeding regime and stocking density for six months and different growth parameters such as body weight, daily weight gain (DWG), specific growth rate (SGR), and proximate body composition were analyzed. The results showed that the hormone treated fish were superior in body weight, weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and protein content comparing with the control group. Also there was a significant increase in male ratio in treated groups and non significant decrease in gonado-somatic index of males comparing with the control. These results of gonado-somatic index (GSI) were confirmable with histological findings of testes of treated groups which include degeneration and vacuolation of seminiferous tubules. The hormone treated fish reflected non significant decrease of plasma total testosterone values. Thus, it is recommended to use 17 α methyltestosterone in producing all male monosex Nile tilapia to obtain more fish production with quick capital cycle and economic product which is safe for human consumption.