Tungsten chalcogenides powders have been prepared by sulfidation of WO3 with gaseous H2S. Different mixed WS2/WO3 systems have been obtained by varying the amount of initial WO3 powder, the time, or the temperature of sulfidation. The samples have been characterized by X-ray diffraction, determination of specific surface area, diffuse reflectance spectroscopy, scanning electron microscopy, and EDX analysis. The photocatalytic degradation of phenol in aqueous suspensions has been employed to test the photoactivity of the powders. The results indicate different behaviors of the samples, depending on the amounts of WO3 and WS2 present in the powders. The coupling and the intimate contact of two different semiconductors with different energy levels is taken into account to explain the enhanced photocatalytic behavior of the mixed systems in comparison with pure WO3 or WS2.