A Na2CO3-carbon nanocomposite (NaC-NC) was prepared from terephthalic acid and NaOH, and its CO2 capture under moist conditions was examined by thermogravimetric analysis and X-ray diffraction. CO2 capture was repeated twice. The first CO2 capture reaction of bulk Na2CO3 was faster than its second, while the second capture reaction of NaC-NC was faster than its first. This may be because of the nanostructural properties of NaC-NC. The regeneration from NaHCO3 to Na2CO3 of NaC-NC proceeded at a lower temperature than with the bulk NaHCO3. Thus, compared with the bulk Na2CO3, we found that NaC-NC could efficiently capture CO2, increasing the reaction rate and decreasing the regeneration temperature.