Polyetheretherketone (PEEK) has been increasingly used as sliding components in engineering. With the attempt to enhance the tribological performance of PEEK under oil lubrication, in the present work, carbon spheres were prepared and then added to lubricating oil as additives. Strikingly, compared with neat oil lubrication, the tribological tests manifest a notable reduction in coefficient of friction (23.5-33.2%) and wear rate (24.2%) under hybrid oil lubrication. Raman spectra, Fourier transform infrared spectra, and energy dispersive X-ray analyses indicate the presence of functional groups on carbon spheres, enabling the good interactions between carbon spheres and lubricating oil. The uniform mixture of carbon spheres and lubricating oil can fill in the gap of the surface irregularities and form a protective boundary film. Additionally, the carbon spheres can result in rolling movement to promote the lubricating performance, evidenced by scanning electron microscopy. This study proposes a simple and practicable approach to improving the tribological performance of PEEK.