To evaluate the effect of phytase supplementation, 300 day-old broiler chicks were distributed to five treatments following a completely randomized design: T1 - Positive Control (PC); T2 - Negative Control 1 (diet with available phosphorus [P], calcium [Ca] and metabolizable energy [ME] lower than PC by 0.15%, 0.18% and 75 kcal/kg, respectively); T3 - T2 + 100 g phytase per ton of feed; T4 - Negative Control 2 (diet with available P, Ca and ME lower than PC by 0.18%, 0.23% and 95 kcal/kg, respectively); and T5 - T4 + 200 g phytase/ ton of feed. Phytase supplementation improved body weight, weight gain and feed efficiency of broilers fed the negative control diets. Significant differences among treatments were observed in % abdominal fat, % leg and % thigh. Higher income over feed and chick cost was obtained in broilers fed diets with phytase compared to those fed the negative and positive control diets. The results suggest that growth performance of broilers fed diets with lower specification in available P, Ca and ME is not adversely affected if phytase is added in the diet.