Polyazeotropy in binary systems is a singular case of vapor-liquid equilibrium (VLE) where, at a given pressure or temperature, various azeotropes of alternating deviations from ideality are observed. Multiple azeotropy can be observed in systems which strongly associate in the vapor phase. Vapor-liquid equilibrium was measured for the 2-methylpropyl ethanoate (1) + ethanoic acid (2) system at 390.15 K and 353.15 K. The system presents two azeotropes at 390.15 K and none at 353.15 K, the polyazeotropic behavior at the higher temperature can be explained in terms of dimerization of ethanoic acid. The data were satisfactorily correlated using excess models for associating mixtures and chemical theory for the treatment of the vapor phase.