The Perturbed Chain Polar-Statistical Associating Fluid Theory (PCP-SAFT) equation of state was for the first time combined with the Density Gradient Theory (DGT) to calculate liquidliquid (LL) interfacial properties of ternary mixtures containing compounds of different polarity. The components involved were decane, dodecene, linear aldehydes (butanal, octanal, dodecanal), N,N-dimethylformamide and propylene carbonate. Besides ternary mixtures, also interfacial properties of binary systems consisting of the aforementioned compounds were studied. As a supplement, liquid densities of the equilibrium bulk phases of the binary and ternary mixtures were investigated. In addition to the modeling of data, LL interfacial tensions were measured using the drop volume method. Experimental density data were generated using a vibration tube densitometer. Investigating the applicability of the model to describe the LL interfacial tensions of binary and ternary mixtures revealed very good agreement between calculated and experimental data. Concerning the estimation of values for parameters within the DGT framework, approaches were suggested which allow the prediction of ternary LL interfacial properties. Furthermore, the model was applied to examine accumulation of compounds at the interface. Thereby, peculiar adsorption effects were observed.