Liquid-liquid equilibria of a ternary system, water + hexadecane + propylene glycol n-propyl ether, were measured at temperatures ranging from (298.15 to 333.15) K under atmospheric pressure. At 298.15 K, the system exhibits only one two-liquid-phase-coexisting envelope in the triangle phase diagram. The system exhibits one three-liquid-phase-coexisting tie triangle and three two-liquid-phase-coexisting envelopes in the triangle phase diagram for the temperature ranging from (308.15 to 333.15) K. The experimental data were successfully correlated with the NRTL model.