Finding the suitable stocking density of Asian seabass reared in recirculating aquaculture system (RAS) is important in aquaculture industry, as high stocking density can bring up economic profit, but low stocking density can induce stress levels of fish in a limited space. The objectives of this study were to compare the growth performance of Asian seabass Lates calcarifer and dissolved oxygen (DO) levels at different stocking densities and feeding rates in RAS. The study was carried out for a period of 56 days in a new RAS at Marine Aquaculture Centre, St John’s Island, Singapore. Asian seabass (51.23 ± 0.14 g) were randomly distributed in 27 tanks (1 m3) at three initial stocking densities: low D1 (5.6 kg/m3), medium D2 (6.7 kg/m3), and high D3 (7.7 kg/m3). Fishes were fed twice daily and received three different daily feeding rates (F1: 3.5%, F2: 4%, F3: 4.5%) for each stocking density. Water quality parameters were monitored, such as DO, temperature, pH, ammonia, nitrate, nitrite, salinity, oxidation-reduction potential and alkalinity. The present study showed the high stocking density group (D3) can be reared up to 33 kg/m3 in the RAS. The stocking densities and feeding rates had no effect on survival and feed conversion ratio (FCR). However, the feeding rates affected the final body weight, weight gain and thermal growth coefficient (TGC). In high stocking density group, high feeding rate (F3) did not improve net fish yield as compared to moderate feeding rate (F2), showing there is a maximum density above which growth is limited, no matter what the feeding rate. The DO levels fluctuated throughout the study and the average of DO level was 7.58 mg/L. Low DO levels (>2 mg/L) were recorded in 5 out of 9 tanks in D3 group after feeding. Principal Component Analysis revealed that increased stocking density influenced the DO levels. This study will be useful for the practitioners to understand the good practice for stocking density in RAS.