Clays and clay minerals are one of the important groups of materials that are widely used in environmental cleanup applications. The natural clay minerals are hydrophilic in nature, and hold high chemical stability and cation exchange capacity. Owing to the native electronegative surface properties and cation exchange capacities, natural clay minerals are good adsorbents of heavy metal cations and many other cationic organic contaminants. The modification of clay minerals can significantly improve their surface properties that consequently increase their contaminant removal capacities and efficiencies. The current chapter presents a brief overview of various clay modification and surface engineering methods, and discusses how the resultant modified clay products can remediate various environmental contaminants.