A feeding trial was conducted to investigate the effect of dietary supplementation of selenium forms (inorganic and organic) on growth performance, feed utilization, hemato-biochemical parameters and hepatic antioxidant enzymes activity of Nile tilapia, Oreochromis niloticus for 70 days. Three isonitrogenous and isocaloric diets (306.6 g kg^-1 crude protein and 20.04 MJ kg^-1 gross energy) were formulated. Each diet was supplemented with selenium forms; control, organic selenium and inorganic selenium. After 70 days, the highest final body weight, weight gain, average daily gain, protein efficiency ratio and best feed conversion ratio were recorded in fish-fed organic selenium. No significant differences (P ≥ 0.05) were found in haemoglobin, hematocrit, and red blood cells compared with the control diet. On the other hand, adding selenium significantly (P ≤ 0.05) decreased the ALT and AST values where the lowest values of ALT and AST were recorded in fish-fed diet supplemented with inorganic and organic selenium. While adding selenium significantly (P ≤ 0.05) increased serum total protein, the best value was recorded in fish-fed organic selenium. Also, the addition of organic selenium (P ≤ 0.05) enhanced the hepatic superoxide dismutase activity and total antioxidant capacity level while; malondialdehyde concentration was significantly (P ≤ 0.05) decreased with addition of organic selenium.  In conclusion, the addition organic selenium in tilapia diet improved the growth performance, feed utilization hemato-biochemical parameters and hepatic antioxidant enzymes activity.