A 3 × 3 factorial feeding trial was conducted to evaluate the effects microbial phytase (MP) supplementation fed with Ca/P ratio on growth, digestibility, vertebral mineralization and some blood parameters in Nile tilapia Oreochromis niloticus. Three levels of phytase (0, 500 and 1000 Ukg-1 diet) were combined with three Ca/P ratios (0.3:1, 0.6:1 and 0.9:1), respectively. The Ca/P ratios were achieved by supplementing calcium propionate at (0, 5 and 10 g kg-1 diet). After a 84-day feeding trial, tilapia fish fed 500 and 1000 Ukg-1 diet at Ca/P ratio (0.6:1) had significantly higher growth rate, feed intake (FI) crud protein, vertebrae ash and phosphorus than other groups. Interaction between Ca/P and MP are significantly (p