The aim of this study was to evaluate the effect of probiotic Bacillus amyloliquefaciens on the growth performance, blood profile and intestinal morphometry in Nile tilapia (Oreochromis niloticus) reared in cages. 936 Nile tilapias were distributed in 12 cages (1.5 m³). Fish were fed for 90 days on basal diets containing 0 (control); 1x10(6) CFU g-1; 5x10(6) CFU g-1; and 1x10(7) CFU g-1 of the probiotic. The results showed no significant difference on performance and proximal composition of fish. Blood glucose and hemoglobin were lower in 1x10(7) CFU g-1 group, suggesting improves of the homeostatic state of the fish. Other hematimetric indices did not differ between groups. It was observed significant increase of villi height and in the number of goblet cells of the intestine in fish supplemented 5x10(6) CFU g-1 and 1x10(7) CFU g-1 of food suggesting that fish improved the digestion and absorption of nutrients. However, more studies are needed to determine the efficacy of this probiotic in field conditions in Nile tilapia.