This study was conducted to investigate the partial replacement of fish meal with defatted peanut meal (DPNM) in diets of Mozambique tilapia, Oreochromis mossambicus and to evaluate its effect on body fatty acids composition. Four levels of DPNM inclusion (0, 10%, 20%, 30% and 40%) were used and one control group was included. Fish diets were isonitrogenous (crude protein 36%) and isoenergetic (20 kJ/kg). One hundred and fifty tilapia fry (average weight of similar to 0.85 g) were fed during a 45-day feeding trial conducted in a recirculation system aquarium. Polyunsaturated fatty acids (PUFAs) in fish fillet showed increasing with increase of DPNM level. The present results suggest that defatted peanut meal is a promising alternative feedstuff and that it could be safely used in Mozambique tilapia diets up to 10% without adverse effects on fillet fatty acid composition.