A serious risk to the wellbeing of terrestrial and aquatic ecosystems is wastewater that contains harmful materials. It is essential to develop toxin-free technologies for wastewater treatment in order to support the sustainable advancement of global civilization. The field of green nanotechnology aims to achieve sustainability in a variety of applications. It also possesses a major influence on the development of greener, cleaner technologies that have substantial positive effects on human health and the environment. Owing to their unique features, nanomaterials (NMs) are currently the subject of extensive research for wastewater treatment. Various types of NMs are utilized for wastewater treatment, depending on the kind of contaminants and the required level of treatment efficiency. Novel and emerging NMs are evolving as the field of green nanotechnology continues to grow. For example, covalent organic frameworks, single-walled and multiple-walled carbon nanotubes (SWCNTs and MWCNTs), metal, and metal oxide-based nanoparticles (NPs) are among the NMs which can be utilized to remediate wastewater. The applications of graphene-based NPs, their oxides (GO), and reduced graphene oxide (rGO) are also extremely promising in wastewater treatment. Higher adsorption capabilities for organic contaminants are demonstrated by ferric oxide. Furthermore, magnetic nano-powder confers a low adsorption capacity for phenols. With excellent adsorption, pyrrolidone-reduced graphene oxide (PVP-RGO)-based NPs have been employed as adsorbents for the removal of inorganic target contaminant copper. Again, it has been demonstrated that zero-valent metal and metal oxide NPs—particularly iron oxides—are more efficient at recovering heavy metals from wastewater than conventional carbon nanotubes (CNTs). This chapter provides a thorough analysis of current developments in common NMs used for sustainable wastewater treatment. This study also evaluates in detail the appropriate uses, potential, and existing constraints of green nanotechnology in wastewater treatment. The novelty of the chapter lies in its review of contemporary applications of different kinds of NMs and related research studies. Such an approach will be helpful to acquire insights into technological breakthroughs, applications, and future problems of nanotechnology deployment for wastewater treatment.