Liquid-liquid equilibrium (LLE) data for the (water + valeric acid + methyl ethyl ketone or methyl isobutyl ketone) ternary systems were measured at T = (298.2, 308.2 and 318.2) K and atmospheric pressure. Solubility curves and tie-line end compositions were determined for the investigated systems. Both ternary systems show type-2 behavior of the LLE systems. The experimental tie-line data were correlated to assess consistency with the Othmer-Tobias and Hand equations. Distribution coefficients and selectivity factors were determined to evaluate the solvent extraction capacity. The maximum of separation factors for methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) as solvent were determined as 96.8 and 469.5 at 298.2 K, respectively, and the separation factors decreased with increasing temperature. As a result, MEK and MIBK have relatively high separation factors and are suitable separating agents for valeric from water. Binary interaction parameters of NRTL and UNIQUAC thermodynamic models were estimated for these systems by using genetic algorithm (GA). The average RMSD values between the experimental and the calculated mass fraction of the NRTL and UNIQUAC models are 0.0021 and 0.0222, respectively. The RMSD values demonstrate that in order to describe the phase behavior of the studied LLE systems the NRTL model is a more suitable model in comparison to the UNIQUAC model.