Novel 3D hierarchical Ag₃PO₄/MoS₂ composites were successfully prepared through a facile and reproducible hydrothermal-in situ precipitation method. The 3D flower-like spherical MoS₂ nanoarchitectures acted as an excellent supporting matrix for the in situ growth of Ag₃PO₄ nanoparticles. The photocatalytic performance of the composites and the effect of the amount of MoS₂ were investigated. The obtained hierarchical Ag₃PO₄/MoS₂ composites exhibited significantly enhanced performance for photocatalytic oxidation of Rhodamine B (RhB) compared with pure Ag₃PO₄ under visible light irradiation. Ag₃PO₄/MoS₂ composites with 15 wt% of MoS₂ showed the optimal photoactivity for the degradation of RhB, which was approximately 4.8 times as high as that of pure Ag₃PO₄. What's more, the optimal Ag₃PO₄/MoS₂ composite also showed better photodegradation efficiency for methyl orange (MO) and p-chlorophenol (4-CP) than pure Ag₃PO₄. More attractively, the stability of Ag₃PO₄ was improved after the in situ deposition of Ag₃PO₄ particles on the surface of MoS₂ nanoflakes due to the conductivity of MoS₂ itself as electron acceptors. The enhanced performance of the hierarchical Ag₃PO₄/MoS₂ composites under visible light was caused by a synergistic effect including the improved separation of photogenerated charge carriers, boosted light harvesting, a relatively high surface area and matching energy band structures between the two components. Interestingly, the heterostructured Ag₃PO₄/MoS₂ composite reduced the use of the noble metal silver, thereby effectively reducing the cost of the Ag₃PO₄ based photocatalyst. Ultimately, a MoS₂ involved photocatalytic mechanism for the hierarchical Ag₃PO₄/MoS₂ composites was also proposed.