Solubility data of carbon dioxide (CO2) (1) in methanol (2), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([omim](+)[Tf2N](-)) (3), and their mixtures (w(3) = 0.2, 0.5, and 0.8) at temperatures 313.2 and 333.2 K and pressures up to 7.0 MPa were measured by a high-pressure view-cell technique. The solubility of CO2 in methanol (w(3) = 0), [omim](+)[Tf2N](-) (w(3) = 1.0) and their mixtures follows the order of (w(3) = 0)<(w(3) = 0.2)< (w(3) = 0.5)<(w(3) = 0.8)<(w(3) = 1.0) at the same temperature and pressure, while the magnitude of Henry's constants follows the reverse order at a given temperature, which is consistent with the COSMO-RS (conductor-like screening for real solvents) calculation. The solubility data of CO2 in methanol and [omim](+)[Tf2N](-) are correlated with the Peng-Robinson equation of state, and the solubility of CO2 in the mixtures of methanol and [omim](+)[Tf2N](-) can be well predicted based on the mole fraction average of methanol and [omim](+)[Tf2N](-) over the solubility of CO2 in pure methanol and [omim](+)[Tf2N](-). The mixtures of methanol and [omim](+)[Tf2N](-) may be used as physical solvents for capturing CO2 with high partial pressures since they combine the advantages of organic solvents and ionic liquids.