Surface engineering has been emerging as one of the most promising technologies to improve the tribological properties of biomaterials with a view to extending the life span of medical implants. For example, some novel surface engineering techniques including ion implantation of ultra-high molecular weight polyethylene (UHMWPE) and thermal oxidation (TO) treatment of titanium alloy have been developed. However, the full potential of improving the wear resistance of orthopaedic implants based on the UHMWPE/ Ti6Al4V system will not be realized until the tribological performance of this surface engineered tribo-system is fully characterized and the acting wear mechanisms are well understood. In this paper, a pin-on-disc tribometer was employed to evaluate the tribological response of the following three tribo-systems: (1) untreated UHMWPE/untreated Ti6Al4V, (2) untreated UHMWPE/TO-treated Ti6Al4V and (3) ion implanted UHMWPE/TO treated Ti6Al4V under water lubricated conditions. Experimental results show that the tribological properties of UHMWPE can be significantly increased by surface engineering its surface and/or the counterface. This can be attributed to the hardened surface of UHMWPE via molecular structure modification induced by ion bean bombardment coupled with the surface oxide layer on Ti6Al4V formed during TO treatment, which has favorable tribological compatibility with UHMWPE.