The application of aluminium in automotive engines requires the material to be strong, stiff and, more importantly, wear resistant, which calls for reinforcement with hard ceramic particles. The resultant wear resistance of an aluminium matrix composite is affected not only by the intrinsic properties of the material but also by extrinsic factors involved in the wear process. Few studies have been conducted on the influence of mating material on the wear resistance of aluminium matrix composites and that of the whole friction couple as a system. This paper presents the results of the pin-on-disk wear tests of a potential piston material, the Al-20Si-3Cu-1Mg alloy reinforced with 10 vol.% Al2O3 particles, with the variation of the hardness of a steel counterface from 28 to 58 HRC. The work shows that the wear rate of the composite is significantly affected by the hardness of the counter-specimen. For a higher wear resistance of the composite, the mating steel should also be harder. A soft steel counterface would result in increased wear of both the composite and the steel, and thus increased total wear of the friction couple. The observed change in wear rate with the hardness of the counter-specimen is associated with the predominant wear mechanism. The work also shows that the friction coefficient of the composite specimen is also affected by the hardness of the counter-specimen, in addition to the pressure applied in the wear tests.