Vapor-liquid equilibrium (VLE) data for methanol + tertbutylamine + N,N-dimethylformamide (DMF) and constituent binary systems containing tert-butylamine at 101.3 kPa were measured. A maximum boiling point azeotrope was observed at the methanol mole fraction of 0.763, corresponding to the temperature of 340.28 K for the binary system methanol + tert-butylamine. The binary equilibrium data were correlated using Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) models, respectively. The VLE data of the ternary system were calculated with the binary interaction parameters of the NRTL model, and the average absolute deviations of the equilibrium temperature and the vapor-phase mole fractions for methanol and tert-butylamine were about 0.87 K, 0.014, and 0.018, respectively. The results show that DMF can break the azeotrope of the methanol + tert-butylamine system as a solvent.