X-ray photoelectron spectroscopy (XPS) was used to characterize the surface films formed on Nb-60Ta-2Zr alloy with an immersion in simulated plasma solution (r-SBF) and human whole blood. Significant difference in the chemical composition and thickness of the oxide films formed on the alloy immersed in these two media was identified. After immersion in r-SBF solution for 24 h, an oxide film of mixed Nb₂O₅ and Ta₂O₅ formed on the alloy surface, while on top of which a 50 nm thick deposition film containing Ca and P could be clearly detected. In contrast, for the alloy immersed in whole blood, only a 24 nm thick oxide film of mixed Nb₂O₅ and Ta₂O₅ existed, but no deposition film containing Ca and P was detected. It was indicated that even though the ion concentration in these two media is nearly identical, the organic components in human blood such as proteins and blood cells may play a role to inhibit the deposition of Ca and P elements.