Wear of ultra-high molecular weight polyethylene (UHMWPE) and its composites is one of the main obstacles that limit the longevity of total joint replacements. Compression molded UHMWPE/quartz composites with organosiloxane as a cross-linking agent for UHMWPE matrix, were tested in nanoindentation and nanowear. The nanomechanical properties of the composite were examined in the light of nanoindentation experiments performed with a diamond tip of nominal radius of curvature of about 150 nm under conditions of various contact loads. Results from nanowear tests show that, in addition to the nanohardness and elastic modulus, the crosslinking procedure has the most pronounced effect on the tribological properties and at 0.5 phr organosiloxane, composites reache their maximum nanowear resistance. These findings are in agreement with the results of conventional mechanical and wear tests performed on these materials.