This study was performed to determine the effect of different fish stocking densities (10 and  20 fish/aquarium) and garlic, Allium sativum level (0, 10 and 20 g/kg diet) as feed additive on the growth performance, body composition and health of Nile tilapia, Oreochromis niloticus juveniles. The experimental fish with initial weight of about 5.06 g was fed diets contained about 30% crude protein and 429 kcal/kg diet as gross energy. The preferable increase of final weight, daily weight gain, specific growth rate, survival rate and feed utilization were obtained by garlic supplementation at 20g/kg diet. Survival rate was not influenced by fish stocking density. The higher body composition as crude protein with moderate ether extract were observed with low density rate of rearing fish fed diets supplemented with 10 g/kg diet of garlic. Heamatological indices explained no hazard effects of both of stocking rate and garlic supplementation on health and liver activity of experimental fish. In general, there were slight differences among both of stocking densities on growth performance, body composition and blood parameters of Nile tilapia juveniles especially with a garlic supplementation. So, it could be concluded that garlic, Allium sativum may be used to enhance the health and growth performance with high stocking rate of Nile tilapia, Oreochromis niloticus fish.