New experimental results are presented for the solubility of carbon dioxide in pure liquid N,N-dimethylmethanamide {= N,N-dimethylformamide, (CH3)(2)NC(H)O, DMF} and in solvent mixtures of (water + DMF) at gas-free solvent mixture DMF mole fractions of about (0.05, 0.1, 0.25, 0.5, 0.75, and 0.9), temperatures of (314, 354, and 395) K, and total pressures up to about 10 MPa. Numerical values are reported for the (molality scale based) Henry's constant of CO2 in DMF and in (water + DMF) liquid mixtures resulting from the new experimental data by applying a common extrapolation procedure. The experimental work is to provide a database for developing and testing thermodynamic models to describe the gas solubility in salt-free and salt-containing mixed aqueous solvents, as well as to test screening methods based, for example, on molecular simulation.