This chapter summarizes the use of green chemistry on the synthesis of nanomaterials as well as their environmental applications. Green routes for the synthesis of nanomaterials are discussed, including those using nontoxic solvents and natural template materials, such as ionic liquid, leaf and tea extract, natural cellulose, sucrose, starch, and plant leaves. Such methods could decrease the use of hazardous chemicals in chemical processes and reduce or eliminate undesirable products during the synthesis process. The employment of micro-organisms for the green synthesis of nanoparticles is also described. In addition, the use of nanomaterials as photocatalysts, Fenton's catalysts, and disinfectants is reported for environmental remediation including the degradation of organic contaminants and the inactivation of pathogenic micro-organisms in water. Finally, the importance of immobilization of nanomaterials onto substrates for their sustainable application to environmental remediation, in particular, contaminated water and wastewater treatment is presented.