Here we report a Bi₂WO₆@g-C₃N₄ core@shell structure which was prepared by a combined ultrasonication–chemisorption method with enhanced photocatalytic degradation. The composites were extensively characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). Compared with bare Bi₂WO₆ and g-C₃N₄, the Bi₂WO₆@g-C₃N₄ composites exhibited significantly enhanced photocatalytic activity for methylene blue (MB) degradation under visible light irradiation. The 3 wt% Bi₂WO₆@g-C₃N₄ showed the highest photocatalytic activity under visible light irradiation, which was about 1.97 times higher than Bi₂WO₆. In addition, the quenching effects of different scavengers displayed that the reactive h⁺ and ˙O₂⁻ play the major role in the MB decolorization. The core@shell hybrid photocatalyst exhibited dramatically enhanced photo-induced electron–hole separation efficiency, which was confirmed by the results of photocurrent and EIS measurements. On the basis of the experimental results and estimated energy band positions, a mechanism for the enhanced photocatalytic activity was proposed.