Stocking density is considered one of the important factors that affect the growth and production of fish. However, information related to the effect of stocking density on the growth performance and production of mono-sex Oreochromis niloticus in pond culture conditions has not been well studied in Ethiopia. Therefore, this study aimed to compare the growth performance and production of mono-sex tilapia at various stocking densities and to determine an ideal and economical stocking density for the culture of mono-sex O.niloticus fingerlings. Male fingerlings were isolated by examination of the genital papilla region and stocked in three stocking densities 3, 5, and 7fingerlings/m in triplicates. The initial mean weight had 26.31 ± 0.06, 26.28 ± 0.08, and 26.33 ± 0.1 g, for 3, 5, and 7fingerlings/m 2 ,respectively, and grown for six months in a 10m concrete pond for each. The gains in weight and water quality parameters were recorded monthly. The final mean weights (±SE) of the fingerlings stocked at densities of 3, 5, and 7 fingerlings were 182.58 ± 0.39, 163.33 ± 0.78, and 153.57 ± 0.34 g, respectively. The specific and daily growth rates for densities of 3, 5, and 7fish were 1.11, 1.05, and 1.01% and 0.9, 0.79, and 0.73 g per day, respectively. The total biomass production obtained at the end of the experiment was 5.11, 7.57, and 9.78 kg for densities of 3, 5, and 7fish/m , respectively. The food conversion ratio (FCR) varied from 2.98 to 3.15, and the best FCR was obtained for 3fish/m 2 (2.98). The dissolved oxygen and ammonia were between 6.7 and 5.08 mg/L and 0.11 g/L to 0.18 g/L respectively. Except for temperature and salinity other water quality parameters showed significant differences between stocking density. The highest net profit was obtained for the stocking density of 7fish/m2. The overall results emanating from this study indicate that even if a higher growth rate was obtained at the lower stocking densities after ending the trial period a high stocking density of 7 fish/m gave a significantly higher yield or production/m 2 and contribute to the highest present of net profit (42%) than 3 fish/m 2 (37.7%) and 5 fish/m 2 (23.9%) and can be very useful to give good returns for local consumption and efficient utilization of resources. Therefore further study should be conducted to investigate better stocking density beyond 7fishes/m whether it will be possible to get more yields per unit area. But need optimum management levels are necessary to fish growth under high-density systems. 2 2 2 2 2 and