Surface modification of titanium has been extensively investigated in implant science and technology in an effort to improve its osteoconductivity. The rate of protein adsorption on titanium surfaces is known to vary depending on the chemistry, structure, morphology, and titanium-specific biological aging of the surface. It is thus desirable to modify smooth titanium surfaces of miniimplants used as orthodontic anchors immediately prior to use. In this study, we have developed a simple surface modification of titanium alloy that improves its biofunctional activity. The surface of a Ti-6Al-4V disk was modified by applying 3% H₂O₂ hydrothermal treatment using an autoclave. A nanostructured porous network TiO₂ was observed on the treated surface. Treated surfaces exhibited higher hydrophilicity, protein adsorption, and cell proliferation than untreated surfaces. 3% H₂O₂ hydrothermal treatment is thought to provide biofunctional activity for aged titanium surface.