Thermal recovery of mono ethylene glycol (MEG) from aqueous streams is one of the most energy demanding operations in industry, because of the large amount of water that needs to be evaporated. The use of alternative technologies such as liquid–liquid extraction could save energy. A new tailor made ionic liquid (IL), tetraoctyl ammonium 2-methy-1-naphtoate [TOA MNaph] was designed in a previous stage of our research on MEG recovery from aqueous streams (Garcia-Chavez et al., 2011) . Here, we report the liquid–liquid equilibrium data for the MEG + water + [TOA MNaph] system at atmospheric pressure for three different temperatures, (313.2, 333.2 and 353.2) K. The experimental equilibrium data was correlated using the NRTL and UNIQUAC thermodynamic models. Both models were able to describe the system adequately, root square mean deviations (RMSD) of 1.34% and 0.89% were obtained respectively.