A facile, green method was developed for the synthesis of stable gold nanoparticles using Peltophorum pterocarpum flower extracts as both reducing and capping agents. The influence of temperature on experiment was studied. The obtained gold nanoparticles were characterized by ultra violet-visible spectroscopy and high resolution transmission electron microscopy. The ultra violet-visible spectroscopy shows the absorbance band around 560 nm, and the high resolution transmission electron microscopy illustrates that the nanoparticles are spherical in shape with size ranging from 5-50 nm.