Copper matrix composites with 3wt% diamond particles were fabricated by powder metallurgy method. Sliding wear behavior of the copper-diamond composites was carried out by using a pin-on-disk wear tester under dry sliding conditions at a constant sliding speed of 100 m/s. The results showed that the wear rate of the composites was significantly lower than that of pure copper. The addition of diamond particles can markedly increase hardness and wear resistance of the copper-diamond composites. For determination of the wear mechanisms of the copper-diamond composites, a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) was employed to observe the microstructure and analyze the chemical compositions of the worn surface. It is found that the main wear mechanisms of the sintered copper-diamond composites were abrasive wear and adhesive wear.