Abstract: This study is aimed at determining the effect of water temperatures on fertilization and hatchability rates of artificially induced Clarias gariepinus. Sixty six (665 broad-stock 132 females and 34 males) were purchased from Agodi fish farm, Ibadan of average weight 398 g and conditioned for two weeks after which some were sacrificed for fresh pituitary hormone and milt. Four trials were carried out. Injection of females was done at different periods of the day (8.00 am, 4.30, 8.00 and 12.00 pm) that is 0800, 1630, 2000 and 2400 h at an average temperature of 26.00, 24.30, 27.66 and 25.00°C, respectively and stripped after 10 h for eggs. Significant variations exist (p<0.05) between water temperature at the time of injection and hatchability/fertilization rates, this is further confirmed by the strong positive correlation of r = 0.95 in both cases. The highest hatchability rate of 77.84% and highest fertilization rate of 66.65% was recorded at 8.00 p.m with water temperature of 27.66°C this is followed by 75.51% at 26.00°C hatchability rate/51.23% fertilization rate for fish infected at 8.00 a.m and stripped 6.00 p.m (10 h later).