The effect of adding lactic acid bacteria (Pediococcus acidilactici) to the diet on water quality, feed utilization, growth, body composition, Hematological parameters, intestinal and liver histology of Nile tilapia, haemato-biochemical parameters, antioxidants, immunological responses, and Enzymatic Activity was investigated. Fish was distributed into Four groups; the control group (T0), T1 group (2.0 g), T2 group (2.5 g), and T3 group (3.0 g) of Pediococcus acidilactici per kg of diet. 25% of Water was changed daily and feed with 31% protein was added three times daily for 56 days. In probiotics-treated groups, growth performance, feed utilization, and fish biomass increased significantly compared to control. The biochemical and immunity parameters (Amylase, Lipase, and Protease activity) and villi height were significantly improved in probiotics groups. In conclusion, adding probiotics to fish diet improved all evaluated parameters