This study aimed to evaluate the effects of diets supplemented with probiotics (Bacillus spp.), prebiotics (chitosan), and synbiotics on the growth performance, innate immune system, antioxidant levels, intestinal community, and food quality of the Nile tilapia over 120 days. Experimental fingerlings (15.5 ± 0.352g) were randomly distributed into 12 rectangular polyethylene tanks, with 60 fish per tank. Four treatments, each with three replicates, were tested: Control, probiotic (Sanolife® PRO-F, Pro), prebiotic (chitosan, Pre), and synbiotic (combination of probiotic and chitosan, Syn). Results showed a significant increase in dissolved oxygen concentration and improved pH levels in the probiotic treatment. Unionized ammonia (NH3) levels were reduced in all treatments compared to the control. The prebiotic-supplemented diet significantly improved the final body weight, final length, weight gain, condition factor, average daily weight gain, specific growth rate, and survival rate. Serum lysozyme activity and nitric oxide levels were higher in all treatments supplemented with probiotics. Additionally, superoxide dismutase (SOD) and glutathione peroxidase (GPX) enzyme levels in the liver were significantly higher in the probiotic group, while malondialdehyde (MDA) levels decreased. The addition of probiotics and the presence of synbiotics increased the total bacterial counts in fish intestines and pond water over four months. Pathogenic Aeromonas hydrophila was identified only in the control group's water during the first month. Escherichia coli and Salmonella were identified in the intestines of the control group in the fourth month. 16S rDNA gene sequencing identified Lysinibacillus sphaericus in the water of the probiotic treatment and Citrobacter freundii in the flesh of the control treatment. Adding Bacillus strains and chitosan individually enhances the growth and health of the Nile tilapia (Oreochromis niloticus).