Benefitting from the principles of photochemical reactions, nanocatalysts play critical roles in the process of the decomposition of pollutants, both organic and inorganic, including plastics, pharmaceutical wastes, pesticides, dyes, and other contaminants of water, soil, and air. The photodegradation processes by nanomaterials often in combination with other photocatalysts have evolved as promising ways of environmental remediation that include nanomaterials comprising metals (e.g., copper, silver, and gold) and metal oxides (e.g., CuO, ZrO2, CeO2, ZnO, and TiO2), semiconducting nanoparticles and quantum dots (such as based on CdSe and CdS), carbon-based nanomaterials (such as graphene, graphene oxide, carbon nanotubes, etc.), metal-organic frameworks (MOFs), and hybrids thereof. In this chapter, the general framework for specific catalyst design, structural characterization, and properties of some highly efficient nanocatalysts will be introduced, and the mechanisms of the nanocatalysis in conjunction with their nanostructural details will be discussed. A brief overview of the nanocatalysts-driven research works related to the photodegradation of organic and inorganic pollutants over the last two decades highlighting the major successes and applicability of the nanocatalysts will be tabulated. Along with a few examples of success stories of using nanophotocatalysts for degrading inorganic and organic pollutants, the challenges in their application and the strategies to be adapted to develop inexpensive, stable, recyclable, and highly efficient photocatalysts will be presented.