Carbon-based nanocomposite materials have been well recognized as versatile functional materials with great potential applications in environment. In this chapter, the techniques applied in fabricating, analyzing, and applying carbon-based nanocomposites are described to address the big environmental challenges faced globally. Additionally, the progress in achieving adsorption capabilities, photodegradation of pollutants, pesticides, and insecticides and energy conversion process using these nanocomposites are discussed. Hybrid structures derived from composite of carbon materials, i.e. carbon nanotubes, graphene, and activated carbon with metallic, polymeric, or ceramic elements are synthesized for a number of environmental applications. It points out functions in water purification, air quality betterment, energy storage, and pollution cleanliness. Environmental effects, sustainability, and scalability of carbon-based nanocomposite are also analyzed in a comprehensive manner. Thus, it clearly emphasizes the central role of nanocomposites in advanced environmental practices and possible future applications of dealing with global environmental problems.