Sulfur-containing gases, like SO2 and H2S are toxic; therefore, experimental data are rare. However, these gases are important in many technical processes, for instance in enhanced oil recovery, where information about the phase behavior and the interfacial properties of mixtures with these gases are required. In this contribution, we investigated these properties theoretically using PCP-SAFT-EOS in combination with density gradient theory. We focus on ternary systems made of sulfur-containing molecules, carbon dioxide and n-heptane representing the oil. With pure component parameters taken from the literature and binary interaction parameters taken also from the literature, except these for SO2 + heptane and H2S + heptane, which were fitted in this work, the phase behavior of the corresponding ternaries over a large temperature and pressure range was predicted. Additionally, the interfacial tension as well as the partial density profiles across the interface were studied. The presence of sulfur compounds leads to a reduction of interfacial tension in comparison with the binary subsystem' CO2 + heptane. Additionally to the predictions polynomial expressions for calculation of surface tension as a function of liquid composition, temperature and pressure are provided in this work. This approach allows the representation of the surface tension of ternary systems very precisely with reduced numerical effort. of