Thymolphthalein was successfully grafted onto graphene oxide nanoplates. The resulting nanoplates were incorporated into polypropylene matrix via solution mixing. State of dispersion of the thymolphthalein-grafted graphene layers in the polymer matrix was examined by field emission scanning electron microscopy (FESEM) analysis and was indicated to be homogeneous. Thermogravimetric analysis (TGA) proved that the nanocomposite is more thermally stable than the neat polymer. The neat polymer and the prepared nanocomposite were converted into thin films by compression molding. Then, the prepared film samples were subjected to oven ageing experiments at 90 ºC. Fourier transform infrared (FTIR) spectroscopy and melt flow index (MFI) measurements carried out on the aged samples revealed that the thermo-oxidative stability of the nanocomposite in the solid state is more than that of the neat polymer. Finally, the obtained results were interpreted in terms of the radical scavenging ability of thymolphthalein moieties of the nanoplates.