Two experiments were conducted to evaluate diet digestibility, performance, digestive parameters, and blood parameters when an enzyme complex (EC) was used in barley- and rye-based diets with different energy levels. In the digestibility assay (exp. I), 108 seventeen-day-old Cobb male broilers were distributed in a completely randomized design in 2 × 2 × 2 + 1 factorial arrangement with two feeds (barley or rye), two EC levels (0% and 0.02%), and two energy levels [3025 and 3125 kcal apparent metabolizable energy (AME)·kg⁻¹], plus a control treatment. In exp. II, 1080 one-day-old Cobb male broilers were distributed in a completely randomized design in 2 × 2 × 2 + 1 factorial arrangement with two feeds (barley or rye), two EC levels (0% and 0.02%), and two energy levels (2875 and 2975 kcal AME·kg⁻¹). No interactions were observed for any variables (exp. I and II). Enzyme complex improved the apparent metabolizable coefficient of gross energy (P = 0.0432) of diets. The EC provided greater weight gain (P = 0.0003) and better feed conversion (P = 0.0025). Intestinal viscosity at 21 d was reduced (P < 0.0001) with the addition of the EC. The EC improved nutrient digestibility and performance, but the effects of energy reduction on performance could not be overcome.