The tribological behavior of polyurethane/epoxy interpenetrating network (PU/EP IPN) composites was investigated aiming at guiding the tevelopment 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.