Nanometer ZrO2 filled polyetheretherketone (PEEK) composite blocks with different filler proportions were prepared by compression molding. Their friction and wear properties were investigated on a block-on-ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The morphologies of the wear traces were observed by scanning electron microscopy (SEM). Results indicated that nanometer ZrO2-filled PEEK exhibited lower friction coefficient and wear rate in comparison with pure PEEK. The lowest wear rate was obtained with the composite containing 7.5 wt % ZrO2. The SEM pictures of the wear traces indicated that the plucked and ploughed marks appeared on the wear scar of pure PEEK, while the scuffing on the wear scar of 7.5 wt % nanometer ZrO2-filled PEEK was obviously abated. Thus, it was inferred that the improvement in the tribological behavior of nanometer ZrO2-filled PEEK composite was closely related to the improved characteristics of the worn surfaces.