In the modern world, the quality of the environment (water, soil, and air) is greatly compromised by numerous pollutants and contaminations from diverse sources. The situation is even exacerbating on daily basis. Tracking and treating the existing contaminants while preventing further pollution may maintain and improve the quality of environment. Clays and clay based nanocomposites provide an efficient and cost effective solution to this end. In this chapter, we begin by introducing clays, composition of clay, clay minerals and various tools used for characterization of clays and clay based nanocomposites. The role of clay based nanocomposites for environmental protection is presented. In particular, the removal of heavy metal ions, toxic organic compounds, hazardous dyes and antibiotics from aqueous environment has been discussed and recent studies are summarized. Purification and remediation of contaminated soil and air with the help of clay based nanocomposites are also discussed.