Liquid-liquid equilibrium (LLE) data of water + butyric acid + {butanal or n-butanol} ternary systems were determined at T = 293.15, 308.15, and 323.15 K and p = 0.1 MPa. The ternary systems investigated display Type I behavior of LLE. Nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) activity coefficient models were applied here to fit the experimental results, and the root-mean-square deviations (RMSD) between experimental data and calculated ones were considered in the calculation. The results indicated that the LLE data were well-fitted with both models, in which the RMSD were less than 0.0124. Moreover, solute and diluent compositions in each equilibrium phase were used to calculate the distribution coefficient (D) and the selectivity (S).