Although it is generally believed that the extraordinarily high molecular weight plays a great role in the excellent wear resistance of ultrahigh-molecular-weight polyethylene (UHMWPE), the mechanism behind this effect remains poorly understood. In this study, we investigated the wear behavior of UHMWPE with respect to its microstructures, measured in terms of its crystallinity, lamellar thickness and crystallite size, entanglement, interphase fractions, and surface roughness. From these structure-property relationships, we conclude that the high wear resistance of UHMWPE can be attributed to its higher degree of entanglement and its high fraction content of interphase domains; the other parameters were either not significant or not relevant. Accordingly, we propose a mechanism in which the more greatly entangled molecular chain networks of UHMWPE protect the surface and subsurface layers from damage under stresses during sliding wear.