Isobaric vapor-liquid equilibria (VLE) were determined for the ternary system methylbutyl ketone + 1-pentanol + nonane and for the binaries methylbutyl ketone + 1-pentanol and 1-pentanol + nonane. Measurements were made in a semi-microebulliometer at the pressures of (26.66, 53.33, and 79.99) kPa. A minimum boiling azeotrope was observed in the 1-pentanol + nonane system. The Wilson and modified Wilson models were used to correlate the binary VLE data. The VLE data of the ternary system were predicted by the modified Wilson model.