The micro/nano-structured CaWO₄/Bi₂WO₆ composite was successfully synthesized by a one-step hydrothermal route without using any templates or surfactants. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry-differential scanning calorimetry (TG-DSC) and Brunauer–Emmet–Teller (BET) theory. The results indicated that the composite has a two-phase composition: CaWO₄ and Bi₂WO₆. The photocatalytic activities of the CaWO₄/Bi₂WO₆ composite were evaluated for the degradation of Rhodamine B (RhB) dye and 4-nitrophenol (4-NP) in aqueous solution under visible-light irradiation (>420 nm), which were 4.5 times and 2.5 times higher than that of the pure Bi₂WO₆, respectively. On the basis of the calculated energy band positions, the mechanism of enhanced photocatalytic activity for the micro/nano-structured CaWO₄/Bi₂WO₆ composite can be attributed to the effective separation of electron–hole pairs.