We developed a single step thermal method to synthesize platinum nanoparticle functionalized graphene sheets (Pt-G) through the thermal treatment of graphite oxide (GO) with platinum acetylacetonate (Pt(acac)₂). The loading concentration of platinum nanoparticles (Pt NPs) on graphene is about 22.3 wt%. We investigate the Pt NP functionalization and the reduction effects of GO by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis and Raman spectroscopy. The results lead to insights into the formation of Pt-G starting from GO upon increasing the temperature. XPS and XRD analysis confirm that the platinum nanoparticle deposition is accompanied by the reduction and exfoliation of GO. Electrochemical studies reveal that Pt-G shows excellent activity and stability towards the methanol oxidation reaction.