Experiments of the fish-shaped phase diagram for the ternary system water + n-dodecane + 2-(2-n-hexyloxyethoxy)ethanol (abbreviated by C6E2 hereafter) under atmospheric pressure were performed at constant water/n-dodecane weight ratio (1/1) to locate the critical end points. The upper and lower critical consolute temperatures for the system of interest are 307.80 K and 282.30 K, respectively. Compositions of two- and three-phase liquid-liquid equilibrium for the ternary system water + n-dodecane + C6E2 at 293.15 K and 303.15 K under atmospheric pressure are presented in this paper.