Farmers must conform to Best Management Practices in fish production such as the development of non-antibiotic dietary supplements for fish growth and health management. We determined the effects of increasing levels of dietary mannan oligosaccharides on growth, immune system and intestine integrity of Nile tilapia. Fish (49.6 ± 10.8 g) were randomly distributed into 12 tanks (250 L; 20 fish per tank) and fed during 60 days with a practical diet supplemented with 0.0, 0.2, 0.4 and 0.6% dietary mannan oligosaccharides (n = 3). Fish growth and immune system were not affected (P > 0.05) by treatments. Fish fed 0.4% prebiotic supplementation presented increased (P < 0.05) intestinal fold height. Moreover, the intestine muscular layer thickness was increased in fish fed 0.4 and 0.6% dietary prebiotic. After 60 days, there were no effects on intestinal morphology. Studies regarding characterization of intestinal microbiota and experiment that reproduce commercial fish production systems hearing conditions are necessary to determine the effective use of this dietary supplement for the species.