The tribological behavior of polyurethane/epoxy interpenetrating network (PU/EP IPN) composites was investigated aiming at guiding the development of polymeric tribo-materials applied in aqueous mediums. Significant improvement of friction and wear, up to 40% and 80%, respectively, was achieved with simultaneous incorporation of SiC submicron-particles and short carbon fibers (SCF). Mechanisms behind this were discussed based on systematic characterization of tribofilms formed on the counterbody, including their chemical composition and tribo-chemical reactions taking place during their growth at the friction interface. With direct evidence, the tribofilms were found to be composed of mainly SiO2, hydrated silica, graphitic carbon and amorphous carbon. Findings of the present study help expand the application of interpenetrating network composites under water lubricated conditions.