The effects of stocking density on oxygen consumption and growth in Nile tilapia (Oreochromis niloticus) under greenhouse conditions were investigated in this experiment. Fingerlings with 1.57 ± 0.14 g mean body weight were stocked in 972 L, rectangular plastic tanks placed inside a polyethylene greenhouse 504 m2, at three densities 90 (T1), 180 (T2), and 270 (T3) ind m-3 (biomass of 0.14, 0.28, and 0.42 kg m-3). Fish were feeding with a commercial diet for Nile tilapia (Api-Tilapia 1, MaltaCleyton® with 50%, protein and 12% lipid) to apparent satiation, three times a day, for 60 days. Fish in each treatment were selected randomly in order to measure aerobic metabolism using closed respirometric chamber technique with constant temperature and volume (1 L). It was found that growth rate of T1 (0.38 g day-1; 4.65% day-1) and T2 (0.21 g day-1; 3.68% day-1) was significantly higher than T3 (0.11 g day-1; 2.67% day-1). Oxygen consumption measurements over 24 h showed that a significant difference exist between treatments T1 = 350 ± 170, T2 = 260 ± 170, and T3 = 200 ± 130 (mgO2 kg-1 h-1). Thus, according to the results the culture of tilapia at a density of 90 ind m-3 can be used for increase production of O. niloticus under greenhouse conditions.