Nutritive value of mesquite ( Prosopis african ) seeds subjected to toasting processing method in the diet of Oreochromis niloticus fingerlings was studied in an 84-day feeding trials. One hundred and twenty all male fingerlings of O. niloticus (5.53 ± 0.01 g) were stocked in triplicate and 4 iso-nitrogenous diets (35 % crude protein) were formulated using the toasted mesquite seed at 0 %, 15 %, 30 % and 45 % inclusion levels to replace soybean meal (SBM) in a completely randomized design (CRD). Proximate composition of the seed was significant ( P < 0.05) on crude lipid, fiber and mineral content of mesquite seed. Essential amino acids profile were differently affected. The anti-nutritional factor tannin and phyate were slightly reduced. The highest weight gain (5.32 g), specific growth rate (1.77 %day -1 ), feed conversion efficiency (0.71) protein efficiency ratio (2.02 %) and economic conversion ratio ($0.91 /kg) were observed in group fed diet I while diet 3 gave the least. Carcass proximate analysis showed high value for crude protein and ash content. Toasted mesquite seed meal could be exploited in the on-farm production of tilapia diet at 15 % inclusion level. Keywords: Mesquite seeds, toasting method, amino acids, nutrient utilization and Oreochromis niloticus . DOI : 10.7176/JBAH/9-14-02 Publication date :July 31 st 2019