In the present research, graphene nanoplatelets/polypropylene (GNP/PP) nanocomposites were prepared by melt mixing and were subjected to accelerated ageing. The effect of graphene on the morphology and physical properties of aged GNP/PP nanocomposites was investigated. The incorporation of graphene to non-aged PP matrix led to changes in its crystal conformation, decreased the ultraviolet-visible (UV-Vis) transmittance and tensile strain and increased the elastic modulus. The ageing of non-reinforced PP increased the β-phase of PP and caused the formation of cracks on its surface, while voids were observed in its cross-section. The aged PP was also characterized by significantly lower UV-Vis transmittance, thermal stability and tensile strain, but increased elastic modulus compared to non-aged PP. Graphene retarded the ageing of PP matrix, according to Fourier Transform Infrared spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) results. In the aged GNP/PP nanocomposite, the morphology did not present any changes and the examined properties were maintained to similar values with that of non-aged GNP/PP nanocomposite.