The critical properties of binary mixtures (acetic acid + ethanol, water + ethyl acetate, and ethyl acetate + ethanol) and ternary mixtures (acetic acid + ethanol + carbon dioxide and water + ethyl acetate + carbon dioxide) involved in the esterification of acetic acid with ethanol were measured using a high-pressure viewing cell with visual observation. Moreover, the critical properties of the nominal reacting mixtures (acetic acid + ethanol + water + ethyl acetate and acetic acid + ethanol + water + ethyl acetate + carbon dioxide) were also determined with the composition representing the extent of reaction (conversion of ethanol or acetic acid) of esterification with the initial mole ratio of acetic acid to ethanol being 1. Such information is essential for determining the reaction conditions when one intends to carry out the esterification under supercritical conditions and/or using carbon dioxide as a solvent, which could be an interesting option to enhance the reaction rate and to increase the equilibrium conversion.