The excess enthalpies for ethanol + acetic acid + ethyl acetate + water system in the chemically equilibrium states are determined with the C80 calorimeter (Setaram) equipped with membrane mixing cells at 313.15 K and atmospheric pressure. The quaternary system exhibited positive values of the excess enthalpies over the entire range of mole fractions. The heat of esterification reaction is calculated on the base of data obtained for heat effects in the mixture, and it was found to be − 3.6 ± 0.2 kJ mol⁻¹. The correlation of the data was carried out using NRTL model and Redlich–Kister equation.