Liquid-liquid and three-liquid-phase equilibria of a ternary system: water + tetradecane + propylene glycol n-propyl ether were measured at (298.15, 308.15, and 318.15) K under atmospheric pressure. The system exhibits one three-liquid-phase-coexisting tie triangle and three two-liquid-phase-coexisting envelopes in the triangle phase diagram at these three temperatures. The experimental data were further correlated with the nonrandom two-liquid (NRTL) model, and the average deviation of compositions was 0.0157 mass fraction.