Carbon, glass, and aramid fiber-reinforced epoxy composites were exposed to oscillatory sliding against various metallic counterparts (steel, aluminum, brass, and titanium) in a flat-on-flat arrangement. The peak-to-peak oscillation width amounted to 700 μm; the contact pressure was 15 MPa. The formation of an interphase layer of wear debris, whose composition was determined by the reinforcing fiber, was found to govern the friction and wear mechanisms. The particulate debris of the glass and carbon fibers are more effective in separating the counterparts than the debris of the soft polymeric aramid fibers. Furthermore, the carbon fiber and, even more, the glass fiber particles act as an abrasive interlayer, which increases water. The abrasive effect of the fiber debris is more detrimental for the softer (aluminum, brass) than for the harder counterparts (steel, titanium).