Bi2MoO6/BiPO4 composites were successfully synthesized via a simple one-pot hydrothermal method. The samples were characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscope and UV–Vis diffuse reflectance spectroscopy. The resulting Bi2MoO6/BiPO4 composites exhibit excellent photocatalytic activity and stability to methylene blue degradation under visible light (λ > 420 nm). The Mo:P = 3:4 sample shows the highest photocatalytic activity at different molar ratios. Different pH values have a considerable effect on the composites. When the pH value is 9, the sample shows the highest photocatalytic activity. The photocatalytic mechanism of Bi2MoO6/BiPO4 composites is mainly due to the higher separation efficiency of electron–hole pairs. A possible pathway of degradation of MB was proposed in this study. The effect of pH on the Bi2MoO6/BiPO4 composites is discussed.