Micelle formation, expressed often via the critical micelle concentration (cmc), is one of the most important properties for aqueous surfactant solutions. In this work, five different versions of the UNIFAC method have been systematically investigated for nonionic surfactants of the water + polyoxyethylene alcohol type. The results show that these five UNIFAC methods qualitatively predict the observed trend of the hydrophobic chain but not that of the hydrophilic chain. It has been established that by introducing a new oxyethylene group (CH2CH2O) and estimating its interaction parameters from vapor-liquid equilibrium data, the original UNIFAC VLE method can provide good prediction for the critical micelle concentration of water + polyoxyethylene alcohol systems, both with respect to varying hydrophobic and hydrophilic parts. Further improvement could be anticipated if the new parameters were refined based on additional ether + water vapor-liquid equilibrium data.