Montmorillonite is a multifunctional clay mineral and a major component of bentonite. Montmorillonite has been used in various industrial and pharmaceutical fields due to its unique characteristics, which include swelling and adsorption. The high adsorption capacity of montmorillonite contributes to increase drug entrapment and sustained-release of drugs. Montmorillonite generally sustains drug release in many formulations by strongly adsorbing to the drug. In addition, montmorillonite enhances the dissolution rate and bioavailability of hydrophobic drugs. Moreover, montmorillonite was applied to form composites with other polymer-based delivery systems. Thus, montmorillonite could be applied to formulate diverse drug delivery systems to control and/or improve the pharmaceutical properties of drugs, including solubility, dissolution rate, and absorption. In this review, perspectives of applying montmorillonite as a pharmaceutical excipient in drug delivery systems are discussed.