Experimental measurements of pressure and temperature are reported over a wide composition range for the phase coexistence of carbon dioxide–benzene–water ternary mixtures. Phase coexistence was observed at temperatures and pressures up to 600 K and 300 MPa, respectively. The experimental measurements were determined largely by a synthetic method which involved determining knick-points in the temperature–pressure curves supported by additional visual observations. The ternary mixtures exhibit both two-phase/one-phase and three-phase/two-phase transitions. The experimental measurements are supplemented by equation of state calculations using the Guggenheim equation of state in conjunction with conformal solution theory and the one-fluid model.