Liquid−liquid equilibrium (LLE) data of the solubility curves for ternary systems of water + pentane-2,4-dione + ethyl ethanoate and tie-line compositions for both of the ternary systems of water + pentane-2,4-dione + ethyl ethanoate and water + pentane-2,4-dione + cyclohexane were determined at (298.15 and 313.15) K and at a pressure of 101.3 kPa. Distribution coefficients were evaluated for the immiscible region. The reliability of the experimental tie-lines has been confirmed by using the Othmer−Tobias correlation. The experimental data were fitted using the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) equations; parameters of these two models were regressed.