Equilibrium tie line data have been determined at 323.15 K, 348.15 K, and 373.15 K for the ternary liquid-liquid equilibria (LLE) of three alkane + butylbenzene + sulfolane systems, where the alkanes studied are decane, undecane, and tetradecane. The relative mutual solubility of butylbenzene is higher in decane + sulfolane than in undecane + sulfolane or tetradecane + sulfolane mixtures. The tie line data were correlated with the UNIQUAC and NRTL models. The calculated values based on the UNIQUAC model were found to be better than those based on the NRTL model. The values of selectivity and the distribution coefficient were derived from the equilibrium data.