The rapid synthesis of platinum nanoparticles using ethylene glycol and microwave dielectric heating is reported here. The Pt nanoparticles after synthesis were transferred to a toluene solution of dodecanethiol (DDT) to form DDT-encapsulated Pt nanoparticles. The TEM examinations showed nearly spherical platinum nanoparticles. The particles were in the size range of 2~8 nm and exhibited narrow size distribution. They were stable in the toluene solution for at least 10 months. Larger particles were formed with longer microwave heating time, higher metal precursor salt concentrations, and lower pH values. XPS measurements revealed >80% of Pt was in the zero valent state and the S 2p signal showed strong adsorption of sulfur species on the surface of platinum nanoparticles. FTIR spectroscopy also confirmed the interactions of thiol groups and the platinum surface.