A diffusion surface layer of Ti3P+Ti-Ni type was produced on Ti6Al4V titanium alloy by a chemical electroless nickel-phosphorous deposition process combined with glow discharge treatment. The microstructure, phase composition, surface topography, corrosion and wear resistance of this surface layer were investigated, as was its biocompatibility with the human Saos-2 cell line. Cells were analysed in terms of cell viability and adhesion. The results showed that the duplex treatment permits production of a layer that has high corrosion and frictional wear resistance and the Ti3P outer zone of this composite layer is characterised by a topography and chemical composition promising high biocompatibility. This new Ti3P+Ti-Ni type layer offers new potential in biomaterials for bone applications in terms of improved tissue ingrowth and long-term use.