Nanocomposite hydrogels have emerged as a promising solution for heavy metal ion removal due to their high adsorption capacity, selectivity, and reusability. This chapter provides an in-depth exploration of the synthesis, characterization, and application of nanocomposite hydrogels integrated with nanomaterials such as graphene oxide, carbon nanotubes, metal nanoparticles, and nanoclays. These advanced materials exhibit enhanced physicochemical properties, including increased surface area, tunable porosity, and mechanical strength, facilitating efficient adsorption of metal ions like lead, mercury, and cadmium. Various adsorption mechanisms, including physical adsorption, chemisorption, ion exchange, and chelation, are analyzed to understand the hydrogel's performance. Case studies demonstrate their effectiveness in diverse environmental scenarios, outperforming conventional methods. Despite challenges such as hydrogel stability and regeneration, ongoing advancements in stimuli-responsive design and integration with other treatment technologies offer innovative solutions. The research underscores the potential for large-scale application and commercialization of nanocomposite hydrogels, contributing significantly to sustainable water purification and environmental remediation.