Tribological performance of diamond-like carbon (DLC) and Si doped DLC (Si-DLC) films on Ti–6Al–4V under bovine serum as well as water and ambient air condition has been studied in terms of surface modification with O 2 plasma treatment for superhydrophilic surface. A tribo-test revealed that bovine serum significantly enhanced the tribological performance on all DLC surfaces in comparison with those under water or in air medium. Especially, O 2 plasma treated Si-DLC coatings with superhydrophilic nature were found to lower the wear and increase coating stability associated with macromolecules especially proteins in the bovine serum and their interactions with surfaces.