Solar energy is the extreme realistic solution to regularly growing energy crisis. Several solar energy conversion systems have been in harnessing into useful form of energy. The performance of solar energy devices depends on the properties of nanomaterial used for solar energy conversion. As the primary sources of energy are depleted increasingly and give rise to the energy and environmental crisis for humankind. Therefore, exploration of FeS2 pyrite nanostructures for energy and environment applications are carried out in this review. This review focuses on the synthesis, functionalization as well as applications of FeS2 nanomaterial. The shape and size control have been governed by the synthesis methods such as hydrothermal method, sulfidation, solvothermal method and hot injection method. All these methods are discussed in detail. The review involves overview of FeS2, also outlining the structure, basic magnetic, optical and transport properties. Then the comprehensive study regarding modification of FeS2 nanostructures is also illustrated. The well synthesized FeS2 nanomaterials have been used for basic building blocks of functional systems and their application in photovoltaics and photocatalysis is briefly reviewed. Lastly, various future strategies and trends in these research areas are outlined.