Friction and wear of motion components operating under harsh lubrication conditions are key aspects that must be considered in vast numbers of applications. In the present work, graphene oxide (GO) functionalized in-situ with ionic liquid (IL) were uniformly dispersed into epoxy (EP) via a two-phase extraction route. In comparison to as-exfoliated GO, GO functionalized with IL (GO-IL) showed significantly improved dispersibility in EP matrix. It was disclosed that the addition of only low-loading GO-IL significantly reduced the friction and wear of EP over whole lubrication regimes, whereas as-exfoliated GO nanosheets played a positive role just under the moderate lubrication conditions. In particular, obvious synergy between the IL and GO was identified when sliding took place under harsh rubbing conditions. Comprehensive interface characterizations provided direct evidence that a nanostructured tribofilm comprising GO nanosheets, IL chemical groups and EP matrix was established. It was surmised that tribofilm growth was constantly fed by molecular species released from GO-IL reinforced EP, while GO digested within the tribofilm enhanced its robustness and improved the boundary lubrication capability. This work opens up new opportunities for formulating high-performance polymer composites for a wide range of applications subjected to harsh boundary lubrication conditions.