Abstarct: In this study, copper-reduced graphene oxide nanocomposites (Cu/RGO NCs) were prepared using plum extract as a reducing agent from copper(II) nitrate and graphene oxide precursors. Then, Cu/RGO NCs was added to the polyvinyl alcohol (PVA) polymer network as a reinforcement and polyvinyl alcohol-copper-graphene oxide nanocomposites (PVA-Cu-RGO NCs) was prepared. Then, NCs were characterized by conventional methods such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction pattern (XRD), scanning electron microscopy (FE-SEM), X-ray energy diffraction spectroscopy (EDS), Ultraviolet-visible spectrophotometer (UV-Vis) and Raman spectroscopy. The thermal behavior of NCs was investigated by TGA-DTA and DSC thermal analyzes. The results showed that by adding reinforcers (Cu NPs and RGO) to polyvinyl alcohol, the glass transition temperature (Tg) of NCs was improved.