The objective of this study was to evaluate the effect of adding different xylanase and ?-glucanase enzyme blends to maize- and soybean meal-based diets on performance and energy metabolizability in broilers. Two experiments were carried out with broilers of the COBB 500 strain. In the first experiment, 1960 chicks were assigned to a completely randomized design with a 2 × 3 + 1 factorial arrangement, totaling seven treatments, namely, T1- Positive control (PC); T2 - Negative control 1 (NC1; PC minus 200 kcal kg-1 ME); T3 - NC1 + Blend A; T4 - NC1 + Blend B; T5 - Negative control 2 (NC2; PC minus 167 kcal kg-1 ME and 5% amino acids); T6 - NC2 + Blend A; and T7 - NC2 + Blend B. Fourteen replicates were used per treatment and 20 birds per experimental unit. The parameters evaluated at 21 and 42 days of age were weight gain (WG), feed intake (FI) and feed conversion (FC). At 42 days, production efficiency index (PEI), viability and the yields of cuts were also calculated. Birds that received diets with a reduced nutritional value showed a reduction in WG and PEI and worsened FC as compared those of PC treatment (p < 0.05). However, the birds that consumed the NC2 diet with Blend B exhibited a similar WG to those in PC group (p > 0.05) from 1 to 21 days of life. For the yield of thigh + drumstick, the factors were statistically similar (p > 0.05) to those observed in the PC birds. In the second experiment, 432 fourteen-day-old chicks were distributed in a completely randomized design with seven treatments, with eight replicates per treatment and six birds per experimental unit. The apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) values were determined. Overall, the NC2 diet with Blend B provided the highest AME and AMEn values; however, NC1 with the same enzyme blend was the treatment which provided the lowest values. The addition of xylanase and ?-glucanase enzyme blends to maize- and soybean meal-based diets improves WG at 21 days as well as PEI in broilers; however, it does not influence the yield of cuts. Enzymes (Blend B) improve the energy metabolization of broiler diets with reduced energy and amino acid levels.