Carbon-based nanocomposites have emerged as promising materials for environmental monitoring due to their unique physicochemical properties, including high surface area, electrical conductivity, and tunable surface functionalities. These nanocomposites, which typically integrate carbon nanomaterials such as graphene, carbon nanotubes, or activated carbon with various organic and inorganic components, offer enhanced sensitivity and selectivity in detecting a wide range of environmental pollutants. This chapter reviews the recent advancements in the advancement and application of carbon-based nanocomposites for monitoring air, water, and soil quality. Emphasis is placed on the mechanisms by which these nanocomposites interact with pollutants, their detection capabilities, and the development of sensor technologies leveraging these materials. Additionally, the environment and health implications of using carbon-based nanocomposites are also discussed, highlighting the need for sustainable and safe approaches in their deployment. The integration of carbon-based nanocomposites into smart sensor networks for real-time environmental monitoring represents a significant step forward in environmental protection and public health safeguarding.