The study was planed to determine the effects of different doses of hormone 17α-methyltestosterone (MT) and different protein level of feeding on masculinization, growth performance and meat quality in Nile tilapia (Oreochromis niloticus). The experiment was conducted in two phase. In phase-I, two experiments were performed in six aquaria (50fry/aqurium) with two replicates. In experiment A, aquarium -1 was used as control in which no hormone was given while in aquaria 2 and 3, the MT were given@ 60 and 70 mg MT/ Kg of feed containing 30 % crude protein. In experiment B, aquarium - 4 was used as control in which no hormone was given while in aquaria 5 and 6, the MT were given@ 60 and 70 mg MT/ Kg of feed containing 40 % crude protein. Both the experiments were run parallel in six aquaria for 30 days. After that, the fry were shifted to 6 earthen ponds (phase-II) in which feed was given without hormones on the same protein level as in phase-1, to monitor their growth performance for 183 days. At the final harvest frequency of males and females was determined by morphomatric characteristics and examination of gonads.