Several studies have pursued using chitosan as a feed additive in aquaculture; however, more research is needed to evaluate its inclusion in nanoform to achieve more effectiveness. Hence, this study aimed to demonstrate the influence of dietary chitosan and chitosan nanoparticles on the Nile tilapia (Oreochromis niloticus) growth performance, histological intestinal morphometry, antioxidant status, and immunology. For one month, fish (average weight: 42.10 ± 0.05 g) were fed diets containing chitosan (1.0 g CS kg^-1 food) and different concentrations of chitosan nanoparticles (1, 3, and 5 g CNP kg^-1 diet), with the basal diet serving as the control diet. In comparison to the control group, all CS and CNP groups showed a significant increase in growth indices (weight gain, specific growth rate, and feed intake) and intestinal morphometric analysis (average intestinal villous length, width, and depth), where the CS, CNP 1, and 3 groups had the highest values. The CNP 1 and 3 diets significantly (P< 0.05) decreased the levels of intestinal malondialdehyde. Moreover, a significant increase in the levels of serum biochemical biomarkers (total protein, albumin, and globulin), immunological parameters (phagocytic activity/index, and NBT), and intestinal antioxidant parameters (total antioxidant capacity and glutathione reduced) were observed in the CNP 1 and CNP 3 groups, followed by CS. The experimental results demonstrated that dietary inclusion of CNP at low concentrations can promote Nile tilapia growth, intestinal morphometry, antioxidant biomarkers, and immunity at an optimal level of 1.0 g kg^-1 diet.