Despite the increasing availability of feed enzymes and a growing interest in soybean meal (SBM) carbohydrates, there is little information on the potential beneficial effects of dietary supplements of enzymes to increase nutritive value. Here we hypothesize that a combination of mannase (polysaccharidase) and protease enzymes could reduce the anti-nutritive effect described in soybean β-manans and consequently increase the degradability of carbohydrates and proteins in diets based on SBM. We assessed the effect of adding mannase and protease to a corn-SBM diet fed to broiler chicks in batteries, particularly on productive performance and nutrient digestibility. Our results showed that neither BW gain nor feed intake was affected. No consistent effects were observed with the individual enzymes (mannase or protease) on the ileal or fecal digestibility of crude protein and crude fat. However, organic matter digestibility and apparent metabolizable energy of diets tended to increase with mannase supplementation. Addition of this enzyme to the diet also reduced ileal microbial flora (as measured by purine base concentration), which indicated that feed enzymes might contribute to the prevention of digestive diseases.