The supplementation of exogenous enzymes in diets is a common practice in the poultry industry. Different enzymes are used to target specific substrates: phytase acts on phytate, protease acts on proteins of peptides, xylanase acts on arabinoxylan, and amylase acts on starch. The utilization of these enzymes results in the release of target substrate hydrolysis endproducts, leading to enhanced digestibility and improved growth performance. Moreover, the introduction of these enzymes has facilitated the inclusion of various feed ingredients containing anti-nutritional factors in poultry diets, thereby expanding the range of available options and reducing feed costs. Despite their different modes of action and substrates, the use of multiple enzymes concurrently has a potential for synergistic or additive effects. This chapter provides a review of the possible modes of action of these enzymes, as well as recent studies investigating the effects of using these enzymes individually and in combination for broiler chickens.