The This study evaluated the effect of levels of garlic powder (0.0, 1.0, 2.0 and 3.0 g.kg-1) added to diets for Nile tilapia on animal performance, villi height and diet digestibility. The rations consisted of pellets and tilapia and were fed to apparent satiation for 60 days. 120 fish, with initial average weight of 4.20 ± 0.4 g, were masculinized and distributed in 24 aquariums of 70L in a randomized design consisting of four treatments and six replications in a closed circulation system with constant aeration. 240 fishes was used for feces collected by an indirect method (Guelph modified system) and estimation of coefficients of apparent digestibility using 0.5 g.kg-1 of chromic oxide as an inert indicator incorporated into the ration. No significant differences in performance related to organ weight, the hepato-somatic index, the viscero-somatic fat index and villi height were observed. However, the apparent digestibility coefficient of rations was negatively affected by the addition of garlic powder. Garlic powder as an additive in rations for Nile tilapia did not provide positive effects as a growth promoter and worsened the digestibility of nutrients among the tested treatments.