The excess enthalpies of the acetic acid–n-butanol–n-butyl acetate–water system in chemically equilibrium states were measured at 313.15 K and atmospheric pressure. Over the entire range of mole fractions, the system displayed positive excess enthalpy values. The heat of the esterification reaction was determined based on the mixture’s heat effects and was calculated to be –4.7±0.3 kJ/mol. The correlation of the data was carried out using NRTL model.