Equilibrium tie line data have been determined at 323.15 K, 335.65 K, 348.15 K, 360.65 K, and 373.15 K for the ternary liquid-liquid equilibria (LLE) of tridecane + (butylbenzene or 1,4-diisopropylbenzene) + sulfolane systems. The relative mutual solubility of butylbenzene is higher than that of 1,4diisopropylbenzene in tridecane + sulfolane mixtures. The tie line data were correlated with the well-known UNIQUAC and NRTL models. The calculated values based on the UNIQUAC model were found to be better than those based on the NRTL model, and showed that the higher accuracy of predictions existed at lower temperature. The values of selectivity and the distribution coefficient were derived from the equilibrium data at different temperatures.