The present experiment was conducted with a view to assessing the optimum dose of 17α-methyl testosterone hormone to produce all male tilapia and effects of stocking density on the growth performance and production of monosex tilapia (Oreochromis niloticus) in hapa for a period of 120 days at Authentic Matshya Hatchery, Mymensingh. After preparing the pond seven days old fry of tilapia (O. niloticus) were stocked at the rate of 4500, 4000, and 5000 fish fry hapa-1 in three treatments of T1, T2 and T3 with mean initial weight of 0.009g. During the trial period of 28 days 60mg MT Kg-1, 55mg MT kg-1, 65mg MT kg-1 hormone mixed feed were used to produce monosex male tilapia. The nursing of the experimental fry was continued for further 3 months with commercial mega feed. At the end of experiment the sex ratio was determined by aceto carmine gonad squashing method. The result of the study showed that fry in treatment T2 exhibit the highest mean weight gain, specific growth rate (SGR day-1), highest survival rate than T1 and T2 treatments. Water quality parameters such as temperature, dissolved oxygen, pH and transparency were found to be within suitable range throughout the experimental period. The mean percentage of male obtained in the experiment 91.43%, 94.28% 90.43% at doses of 60, 55 and 65mg 17α- methyl testosterone per kg of feed respectively. The dose of 55 mg 17α- methyl testosterone per kg of feed in treatment T2 was found to be best for sex reversal in O. niloticus resulting 94.28% male in the population and the growth rate is highest at the density of 4000 fish hapa-1.