Tie-line data were determined for the systems (water + N,N-dimethylacetamide + 1-pentanol) and (water + N,Ndimethylacetamide + 1-hexanol) at the temperatures of 298.15 and 308.15 K under 101.1 KPa. The phase diagrams for these systems are of type I according to the Treyball classification. The thermodynamic consistency of the measured tie-line data was verified using the Hand and Othmer-Tobias equations. The distribution ratios (D) and selectivity (S) values were computed according to the measured tie-line data to assess the extracting behaviors of the selected solvents. The experimental data were correlated using the nonrandom two liquid and the universal quasichemical activity coefficient equations and the Elephant Herding Optimization Algorithm (EHA). EHA is an emerging nature-inspired stochastic global optimization method, and it has been used for liquid-liquid equilibrium (LLE) parameter estimation of local composition models in multicomponent mixtures. The performance of this new swarm-based metaheuristic search method for LLE modeling with and without the closure equation has been analyzed.