In this study, vapor-liquid equilibria data have experimentally been measured for systems water + triethylene glycol (TEG) and water + TEG + toluene at 85 kPa and various temperatures. The VLE data were determined in a modified Othmer still, and the samples were analyzed using gas chromatography and titration methods. The NRTL, UNIQUAC, and Van Laar models were used to correlate the data. The results demonstrate the enhancement of volatility of water in water + TEG solutions and increasing the purity of the dehydrated TEG by the addition of toluene. Using this method, the more concentrated TEG can be obtained in the stripping columns of the natural gas dehydration systems.