A facile electrostatic self-assembly way was developed to prepare Cu nanoparticles @ rGO (reduced graphene oxide) nanosheets to enhance the properties of PI (polyimide) composites. Through the electrostatic self-assembly between Cu and rGO, interface compatibility of Cu and PI matrix was improved. Meanwhile, the zero-dimensional Cu and two-dimensional rGO in core-shell Cu@rGO hybrids could integrate the multiple advantages and provide synergistic enhancement for PI composites. As a result, the maximum thermal decomposition temperature of PI/Cu@rGO composites recorded an increase of 12 °C in comparision with that of pure PI. In addition, the Cu@rGO hybrids demonstrated the optimal lubrication properties for PI matrix compared to individual Cu, rGO and Cu/rGO blend. For PI/Cu@rGO-0.5 wt% composites, the specific wear rate and average friction coefficient were decreased by 44.1% and 11.6%. The outstanding tribological performance of PI/Cu@rGO composites can be ascribed to the synergistic enhancement between Cu nanoparticles and rGO nanosheets as well as the formation of high-quality transfer film. Furthermore, the inherent abrasion mechanism of PI/Cu@rGO composites was explored systematically.