A simple and fast synthesis method of gold and silver nanoparticles without any surfactant or reducing agent has been developed by using the extract of green tea ( camellia sinensis ) under microwave irradiation. The synthesized gold and silver colloidal nanoparticles were spherical in shape and have an average diameter of 13 and 17 nm for Au and Ag nanoparticles, respectively. The as-synthesized nanoparticles were characterized by TEM, XRD, XPS, and UV-visible spectroscopy.