Liquid-liquid equilibrium (LLE) data of water + acetic acid + dimethyl glutarate were measured at T = (298.2, 308.2, and 318.2) K. Complete phase diagrams were obtained by determining binodal curves and tie lines. The reliability of the experimental tie line data was confirmed by using the Othmer-Tobias correlation. UNIFAC and modified UNIFAC models were used to predict the phase equilibrium data in the ternary system. Distribution coefficients and separation factors were evaluated for the immiscibility region.