Poly(ether ether ketone) (PEEK) composites reinforced by short carbon fibers (SCFs) and nanoscale zirconium dioxide (ZrO2) particles were prepared by twin-screw extrusion compounding and subsequently injection molding. The effects of SCFs and ZrO2 nanoparticles on the mechanical properties and wear behavior of PEEK composites with water lubrication were investigated. The mechanical properties of the composites were dramatically enhanced by the incorporation of SCFs. The addition of nano-ZrO2 also promoted efficient improvements in the stiffness and hardness but degraded the impact strength. The compounding of the two fillers remarkably improved the wear resistance of the composites under aqueous conditions and especially under high pressures. The excellent wear resistance of the PEEK/carbon fiber (CF)/ZrO2 composites under aqueous conditions was revealed to be due to a synergy effect between the ZrO2 nanoparticles and CFs. The SCFs carried the majority of the load during a sliding process and prevented severe wear of the matrix. The incorporation of nano-ZrO2 efficiently inhibited CF failure by reducing the stress concentration on the CF interface and the shear stress between two sliding surfaces via a positive rolling effect of the nanoparticles. Furthermore, a linear correlation was found between the wear rate and some mechanical properties of the composites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1711-1720, 2011