In this work, liquid liquid equilibrium (LLE) data for ternary system water + butyric acid + diisopropyl ether (DIPE) at atmospheric pressure and temperatures of 298.15 K, 313.15 K, and 323.15 K were experimentally measured. From the resulted distribution coefficient and selectivity, we can find that diisopropyl ether is an efficient solvent to extract butyric acid. The reliability of the experimental tie-line data was ascertained through the Othmer-Tobias and Hand equations. The consistency of experimental tie-line data was confirmed by the NRTL and UNIQUAC models. Both models describe the phase behavior of the studied systems accurately with very small average deviations.