A nanocrystalline TiZrN graded coating was deposited on biomedical titanium alloy by DC reactive magnetron sputtering process. The microstructure and compositions of the coating were characterized by XRD, TEM and EPMA. The electrochemical corrosion and bio-tribocorrosion behavior of the coated titanium alloy under open circuit potential (OCP) and applied potentials (−0.15 V ~ +0.25 V) were investigated in Hank's solution with and without 25% calf serum. Compared with TiN coating, the hardness of TiZrN coating is greatly increased due to the Zr solid solution strengthening and nanocrystalline strengthening. Under the conditions of OCP and applied anodic potentials, the TiZrN coated Ti alloy exhibits significantly improved anti-tribocorrosion and anti-friction performances, which are attributed to that the stable Ti and Zr oxide or oxynitride passive film on coating near surface and the increased mechanical properties of the coating decrease the synergistic effect of corrosion and wear. 25% calf serum in Hank's solution enhances the chemical stability of the TiZrN coating through adsorption and bio-lubrication mechanism, and therefore further improves the tribocorrosion performance of the coated Ti alloy. •Nanograin TiN and TiZrN coating are deposited on Ti alloy by PVD method.•TiZrN coating has better anti-tribocorrosion performance than TiN coating.•Synergistic effect of corrosion and wear promotes the damage of TiZrN coating.•Calf serum improves friction and wear performances of the coated Ti alloy.