We report the photothermal properties as well as the in vitro cell test results of titanium oxide nanotubes (TiO2 NTs) as a potential therapeutic agent for cancer thermotherapy in combination with near-infrared (NIR) light. TiO2 NTs are found to have a higher photothermal effect upon exposure to NIR laser than Au nanoparticles and single-wall carbon nanotubes, which have also attracted considerable interest as therapeutic agents for cancer thermotherapy. The temperature increase of a TiO2 NT/NaCl suspension during NIR laser exposure is larger than that of a TiO2 NT/D.I. water suspension due to the heat generated by the formation of Na2TiF6. According to the in vitro cell test results the cells exposed to NIR laser without TiO2 NT treatment have a cell viability of 96.4%. Likewise, the cells treated with TiO2 NTs but not with NIR irradiation also have a cell viability of 98.2%. Combination of these two techniques, however, shows a cell viability of 1.35%. Also, the cell deaths are mostly due to necrosis but partly due to late apoptosis. These results suggest that TiO2 NTs can be used effectively as therapeutic agents for cancer thermotherapy due to their excellent photothermal properties and high biocompatibility.