The study was conducted to evaluate the effect of different stocking densities on growth performances and production potential of monosex tilapia (Oreochromis niloticus) under cage culture conditions for a period of 120 days from 20 August to 16 December 2016 in Dekar haor of Sunamganj district. Three stocking densities under the experiment were maintained viz. 35, 40 and 45 fish m-3 and designated as treatment 1 (T1), treatment 2 (T2) and treatment 3 (T3), respectively and each having three replicates. Stocked fry of tilapia were fed commercial floating diet at a decreasing rate of 10-5% of body weight at thrice daily until the previous day of harvest. Average initial weight of the fingerlings was 11.0 g. Water quality parameters like water temperature, transparency, dissolved oxygen, pH, total alkalinity and ammonia nitrogen were found within favourable aquaculture range. Survival rate of tilapia varied from 91.40 to 96.10% and the highest survival rate was found in T2 (96.10%) followed by T3 (95.40%) and T1 (91.40%). Gross yield of tilapia obtained from all treatments ranged from 5.60 to 6.50 kg m-3 with the highest yield (6.50 kg m-3) in T2 and the lowest yield (5.60 kg m-3) in T1. Daily weight gain of tilapia was recorded as 1.36, 1.31 and 1.10 g in T1, T2 and T3, respectively. The highest (Tk. 383.94 m3) net profit obtained in T2 followed by T3 (Tk. 337.10 m-3) and T1 (Tk. 285.91 m-3). Cost benefit ratio (BCR) was also the highest in T2 (1.97) and the lowest in T1 (1.74). Result of the study indicates that tilapia stocking density of 40 no. m-3 is better among three treatments in respect of survival rate, growth, fish yield and economic return. Therefore, the farmers could be suggested to rear tilapia at lower stocking density (40 no. m-3) in cages to get higher growth, survival and production in a short period of time.