Bentonite clays are widely utilized in many applications associated with controlling the flow properties of liquids due to their unique abilities to swell upon interaction with water. However, controlling the extent to which the clay interacts with water can be a key element in tailoring its use in some applications. While cationic surfactants are widely used for this purpose, employment of other cationic species, such as ionic liquids, can offer utility, especially where less permanent treatments may be desired. In this study, bentonite clay has been modified with the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate (1E3MES). Effects on associated properties, including flow behavior, liquid sorption, and water vapor adsorption/desorption, were studied. It was found that 1E3MES exhibited multilayer adsorption on bentonite. Interaction of the ionic liquid with the clay significantly altered the associative properties in aqueous dispersions as well as significantly changed the adsorption/desorption behavior of water vapor.