Tubular titanates (T-TiO2) are interesting materials considering their large specific surface area and ability for cationic substitution in the tubes. In this study, we systematically examined the alkali-metal ion-exchange features of T-TiO2 and clarified their CO2 adsorption properties at room temperature in details. Assuming the resulting ion exchange was affected by hydration, T-TiO2 ion-exchange samples exhibited more intense exchange levels with an increasing alkali-metal ionic radius. Furthermore, the alkali metal ions exchanged were confirmed from the EDS maps to be uniformly distributed in the samples. CO2 adsorption capabilities were found to decrease with increasing the ionic radius of the alkali-metal ions exchanged. We rationalized the electrostatic forces between CO2 and the alkali-metal ion-exchanged titanate nanotubes as the dominant driving force.