This study evaluated the use of fermented mango (Mangifera indica) seed meal (FMS) to substitute yellow maize in the practical diet for Nile tilapia, Oreochromis niloticus fingerlings (4.76±0.32 g). Five iso-nitrogeneous (35% crude protein) and approximately iso-energetic (3400 ME Kcal/kg) dietsin which yellow maize was replaced by FMSat 0% (FMS0/Control diet), 25% (FMS25), 50% (FMS50), 75% (FMS75) and 100% (FMS100) levels were formulated. The fish were fed on the diets at 5% body weight for 84 days. Alkaloids were highest (2.32%) among the anti-nutritional factors analyzed in FMS, while oxalate (0.84%) was lowest. Potassium was highest (8.91 mg/g) among the minerals, while copper was lowest (0.01 mg/g). Weight gain, specific growth rate and feed conversion ratio were similar (p>0.05) in fish fed diets FMS0 and FMS50. The fish fed diet FMS0 had the highest protein efficiency ratio (1.88). Protein digestibility decreased (p<0.05) as dietary FMS increased, while carbohydrate digestibility gave an inverse relationship. Results obtained show that FMS could replace yellow maize at 50% level without affecting growth, nutrient utilization and apparent protein digestibility in diets for Nile tilapia fingerlings