Liquid-liquid equilibria (LLE) of the multi-component system of water + 2,3-butanediol + oleyl alcohol were studied under atmospheric pressure and at temperatures 300.2, 307.2 and 314.2 K. The mutual oleyl alcohol + water solubility with the addition of 2,3-butanediol was investigated. The system studied formed a type I liquid-liquid phase diagram. The results were used to estimate the interaction parameters between each pair of components in the system for the UNIQUAC activity coefficient. The UNIQUAC model fitted the experimental data with an average root mean square deviation (rmsd) of 3.38%.