Liquid-liquid equilibrium (LLE) of a ternary mixture of water, 2,3-butanediol, and 4-methyl-2-pentanol has been measured at three different temperatures (298.2, 308.2, and 318.2 K) under atmospheric pressure. The experimentally measured solubility and tie line data for the two-phase system were used to construct a ternary phase diagram at each temperature. With the experimental data, the distribution coefficients and separation factors were also calculated and Othmer-Tobias and Hand plots were used to verify the consistency of the measured data. The universal quasichemical (UNIQUAC) and non-random-two liquid (NRTL) models were used for the LLE, and the root mean-square deviation values between the calculated and experimental data were less than 1.21% by the UNIQUAC model and less than 1.96% by the NRTL model, indicating that both model calculations provide excellent agreement with the experimentally measured LLE data in the present study.