A total of 210 day-old male Cobb broiler chickens were randomly assigned to six treatments in a 3 × 2 factorial design. The treatments consisted of three levels of maize: 250 g/kg (LM), 500 g/kg (MM) and 750 g/kg diet (HM) and two levels of enzymes: plus enzyme and no enzyme. Each treatment was replicated five times, with seven birds per replicate. Chickens were reared in multi-tiered brooder cages to 21 days of age in a climate-controlled room. Feed and water were provided ad libitum. Over the feeding period (21 d), there was an increase in feed intake as maize inclusion level (MIL) increased in diets, while supplementation with microbial enzyme improved feed intake only in the MM diet. There was an improvement in live weight (LW) in chickens with increased MIL in their diets. The microbial enzyme supplement also improved LW, but only on the MM diet. The feed conversion ratio (FCR) was improved with increase in MIL in diets, but the enzyme supplements had no effect on FCR up to day 21. At day 21 there was an increase in relative weight of the small intestine with an increase in MIL, but this was not affected by enzyme supplementation. The weight of the liver increased with increase in MIL and enzyme supplementation. At day 21 the pH of the digesta in the gizzard declined with an increase in MIL in diets. In general, there was no significant effect of MIL or enzyme supplementation on pancreatic tissue protein content, chymotrypsin amidase activity and ileal digestibility of protein, gross energy and starch at 21 days of age. The population of Clostridium perfringens decreased significantly with increase in MIL, but other microbial species were unaffected. The present findings suggest that maize could be included at much higher levels than is currently done without detrimental effects on productivity. Exogenous enzymes also resulted in a significant increase in some of these variables.