This study was conducted to investigate the effect of increasing water temperature on growth performance, feed intake, feed conversion ratio, and sex ratio of Oreochromis niloticus. Two groups of O. niloticus fries (3 days post-hatching) were reared in an indoor system, at 30°C and 34°C. In the second group, the water temperature was increased to 36°C for only four hours a day, for the first 25 days of the experiment. At the end of the experiment, the values of body weight, length, specific and daily growth rates, and feed intake were comparable but slightly higher at 30°C. The feed conversion ratio was better in the control tank (30°C) than in the experimental one (36°C). Condition factor was higher than 1 at both temperatures indicating the general well-being of fries along the study period. The sex was skewed towards males under the effect of high temperature (36°C) in the experimental tank.