The esterification kinetics of phthalic anhydride with ethanol was investigated in the isothermal reactor in the presence of sulphuric acid as a catalyst. The investigations were carried out for three different temperatures: 373 K, 393 K and 413 K, within one initial substrate molar ratio (phthalic anhydride-ethanol) equal 1:6. The values of reaction rate have been determined on the basis of empirical equation describing experimental data. The calculated values of reaction rate were introduced into kinetic equation to estimate appropriate parameters. On the basis of Arrhenius and van't Hoff relations activation energy of the reaction and its enthalpy was calculated.