The goal of this work is to provide a purely predictive method for the computation of phase equilibria of mixtures involving fish oil and supercritical carbon dioxide. For this purpose, the Huron-Vidal first-order (MHV1) and second-order (MHV2) mixing rules have been investigated in order to combine the Soave-Redlich-Kwong equation of state with different excess Gibbs energy based models, such as the linear UNIFAC/UNIQUAC, the modified UNIFAC/UNIQUAC, and the Van Laar models. For the mixture b parameter of the equation of state, a linear and a van der Waals like quadratic expression have been considered. The approach that has yielded the most satisfactory results over a wide temperature and pressure range is the MHV1 mixing rule used together with the modified UNIFAC model and a quadratic expression for the mixture b parameter with a universal constant for all investigated systems (saturated and polyunsaturated free fatty acids/fatty acid methyl or ethyl esters in supercritical carbon dioxide). The UNIFAC group interaction parameters involving carbon dioxide and fish oil related compound groups have been estimated using binary vapor-liquid equilibrium data. For the investigated systems, the MHV1 and MHV2 mixing rules were found to give satisfactory predictions considering the quality of the experimental data.