The study of the liquid-liquid equilibrium (LLE) between 2,6-lutidine, 2,6-lutidine-N-oxide and water is important since it has the potential to influence the overall rate of the N-oxidation reaction involving these chemicals. The hydrogen peroxide, which is used as an oxidant to convert the lutidine into N-oxide, decomposes vigorously in a phase separated mixture affecting the overall safety of the process. In the current work, the UNIQUAC activity coefficient model was used to estimate the biphasic compositions and predict the LLE curve for the ternary mixture. The energy parameters used in the equations, which describe the intermolecular interactions were calculated based on molecular simulations. Apart from this, the molecular parameters for N-oxide were obtained by following a quantum mechanical approach, which utilized the GEPOL algorithm to construct the molecular surface. The results predicted by the model provide a satisfactory representation of experimental data at T = 383 K. In addition to this, the influence of temperature on the phase behavior was studied by generating phase equilibrium data at T = 373 and 398 K.