The effects of proton irradiation on the tribological performance of polyimide (PI) composites filled with carbon nanotubes (CNTs) were explored. The results demonstrate that incorporating CNTs into PI decreased the friction coefficients of the composites after they were exposed to proton irradiation. In particular, the addition of 1.0 wt% CNT reduces the friction coefficient by up to 58.8%, which is attributed to the generation of a protective tribofilm. Further analysis of FIB-TEM images demonstrates that polymers and hydrogenated amorphous carbon promote the tribofilm growth, and improve the lubrication properties of the composites. Whereas, the proton radiation-induced mechanical changes result in the poor wear resistance of the PI composites.