Liquid–liquid equilibrium (LLE) data for the ternary system composed of diethyl carbonate (DEC) + 1-propanol + water were measured under atmospheric pressure (101.32 ± 1 kPa) at temperature range of 303.15–333.15 K. The equilibrium data were found to be consistent with the Bachman–Brown method. The data were further correlated with the nonrandom two-liquid (NRTL) and the universal quasi-chemical (UNIQUAC) models, and 0.37% root-mean-square deviation was obtained between the experimental and calculated phase composition. Distribution coefficient and separation factor for this ternary system were calculated from the experimental data.