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Vapor−liquid equilibrium data (water activity, vapor pressure, osmotic coefficient, and activity coefficient) of binary aqueous sodium tungstate solutions and ternary aqueous sodium tungstate−poly(ethyleneglycol) (PEG) solutions were obtained through the isopiestic method at T = 298.15 K. Density and speed of sound measurements were carried out on sodium tungstate in pure water and in aqueous solution of mass fraction 0.02 PEG at T = (288.15 to 308.15) K at atmospheric pressure. From the experimental density and speed of sound data, the apparent molar volume and isentropic compressibility values were evaluated and fitted to the Pitzer equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at infinite dilution were calculated at each temperature. The results show a positive transfer volume and isentropic compressibility of sodium tungstate from pure water to an aqueous PEG solution. Furthermore, experimental refractive index data were measured for solutions of sodium tungstate in pure water and in aqueous solution of mass fractions 0.02 and 0.04 PEG as well as those for solutions of PEG in pure water and in aqueous solutions of mass fractions 0.02 and 0.04 sodium tungstate at T = 308.15 K.