Polymer-clay nanocomposites (PCN) are the most important nanomaterials of the current decade with wide range of applications. Montmorillonite, vermiculite, sepiolite, laponite, bentonite and attapulgite are the main classes of clay used as reinforcement in polymer nanocomposites. Clay nanocomposites show characteristic features of thermal stability, flame retardancy, barrier and anticorrosive properties. This work comprehensively review current developments and applications of polymer-clay nanocomposites in automotive, sporting goods, coating technology, packaging, insulation, building construction, electrochemical, biomedical and environmental. This work also aims to describe the importance of polymer clay nanocomposites in various fields, especially for environmental applications. Polymer clay based nanocomposites also have the potential to decontaminate and remediate aqueous systems, therefore purification and remediation of contaminated soil and air with the help of clay based nanocomposites have also been discussed.