The concern towards the increasing challenges in water treatment technologies made researchers towards significant innovations in recent years. The incorporation of nanotechnology in this field obtained remarkable results due to its exceptional properties. Among them, carbon nanocomposites (CNCs) have proved to be promising materials due to their large surface area, enhanced processibility, stability, synergetic properties, cost-effectiveness, and less impact on the environment. The transformation of CNTs to CNCs by functionalization involves physical/chemical modification of CNTs that improves the capability of CNCs in wastewater treatment technologies. This chapter discusses various synthesis methods, tailored characteristics, spectacular properties, and different functions of CNCs in water treatment. The comprehensive focus is extended on the effective CNC based wastewater treatment technologies of three main classes such as adsorption, desalination, and disinfection. Finally, the concerns of CNCs in environmental health and safety in the direction of future research are discussed. © 2021, Springer Nature Singapore Pte Ltd.