While the fact that heavy metals are frequently occur in minute quantity in natural streams, the abundance of heavy metal ions are much dangerous for human survival and aquatic life at their very low concentrations. Nanotechnology and nanomaterials have put out the interest of experts as a long-term solution to water pollution. Researchers are working to create innovative, commercial nanomaterials for application in water/wastewater remediation. Nanomaterial adsorbents are very advantageous for removing the heavy metal ions because of their huge specific surface areas and improved active sites for pollutant adsorption. The chapter addresses nanomaterial adsorbents, including synthesis techniques, nanomaterial kinds, factors affecting nanomaterials adsorption, as well as future problems. Chemical Vapor Deposition was discovered to be the most effective in providing required properties among various synthesis processes. The optimal removal capacity of some nanomaterials such as graphene composites and cellulose-based nanomaterials has been reported1989 mg/g for Hg(II) and 1641 mg/g for Cd(II), respectively. Other factors are also played an important role (such as contact time, effect of pH, adsorbent dose, temperature, and ionic behavior of metal ions) to remove toxic metal ions in large amount from aqueous waste. Moreover, nanomaterials have been proven as a promising adsorbent for adsorption of heavy metals ions.