In this work, the results of the experimental study of the chemical equilibrium in both homogeneous and heterogeneous areas for the system acetic acid−n-amyl alcohol−n-amyl acetate−water at 323.15 K and atmospheric pressure are presented. The chemical equilibrium compositions and compositions of coexisting liquid phases were determined by gas chromatography. The obtained compositions were plotted in a composition tetrahedron for better clarity. The tie-lines of the heterogeneous chemical equilibrium were presented in transformed variables (the α-variables). The peculiarities of the surface of the chemical equilibrium are discussed. The obtained data are compared with the literature information at 318.15 K. The value of the thermodynamic constant of the chemical equilibrium was estimated using three approaches: an empirical equation, the UNIFAC model, and the quantum chemical calculation.