A total of 480 one-day-old male Ross 308 broilers with an average initial body weight (BW) of 42 ± 1 g was randomly divided into four treatments (8 replicates/treatment, 15 birds/replicate) by their BW to evaluate the influence of a cocktail of protease and xylanase in different energy density of corn- and soybean-meal-based diet on broilers. This experiment lasted for 35 d and there were two phases; starter (1–18 d) and finisher (19–35 d). The experiment was a 2 × 2 factorial arrangement with two levels of metabolizable energy and the cocktail enzyme with 200 mg of protease kg^-1 diet and 100 FXU xylanase kg^-1 diet. Both high-nutrient density and cocktail enzyme supplementation increased (P < 0.05) the body weight gain (BWG) during day 1–18 and day 1–35 as well as dry matter retention on day 35. Broilers fed the high-nutrient-density diets had higher (P < 0.05) energy retention on day 35 and relative breast muscle weight. Broilers fed the cocktail enzyme diets significantly increased nitrogen (N) retention and decreased the levels of ammonia (NH₃) and hydrogen sulphide (H₂S) emission. In conclusion, dietary supplementation of the cocktail enzyme component improved BWG, N retention, and reduced excreta noxious gas emission in broilers.