Isobaric vapor-liquid equilibrium (VLE) at 100 +/- 0.1 kPa for the binary and ternary systems with 2-ethoxyethanol + ethylbenzene + dimethyl sulfoxide (DMSO) was determined with a modified Othmer still. All of the binary VLE data passed the Herington test and the Wisniak test. It was determined that 2-ethoxyethanol and ethylbenzene form a binary azeotrope at 127.4 degrees C, 483 mol % 2-ethoxyethanol at 100 +/- 0.1 kPa. By adding DMSO as a solvent at 0.50 mass fraction, the binary azeotrope of 2-ethoxyethanol and ethylbenzene was broken successfully. The binary VLE data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) models with minor deviations. The correlated binary interaction parameters were then used to predict the ternary VLE behavior, which fit well with the experimental data. These results provide a theoretical basis for the separation of a 2-ethoxyethanol and ethylbenzene mixture with DMSO as a promising solvent in extractive distillation.