In the present study, nanostructured CaWO4 photocatalyst was successfully prepared via a simple chemical method. The obtained product was characterized by X-ray powder diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray, and UV–Vis diffuse reflectance spectroscopy. The XRD pattern showed that the CaWO4 powder presented a scheelite-type tetragonal structure. The photocatalytic activity of nanostructured CaWO4 was evaluated by degradation of methylene blue (MB) in aqueous solution under direct sunlight irradiation. The effect of the initial pH of the solution on the photocatalytic degradation performance was investigated. The results showed that the photocatalytic reaction followed first-order kinetics and the sunlight photocatalytic efficiency of the sample increased with increase in pH. The rate of MB photodegradation under sunlight at pH 10 was markedly higher than at pH 6 or 8. A maximum of 98 % decolorization of MB was achieved at pH 10 after 3 h of natural sunlight irradiation.