Ag3PO4 dodecahedrons were post-treated by chemical etching with ammonia solution. The etched samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 sorption, UV-vis diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), photoluminescence (PL) and photocurrent experiments. The SEM results showed that upon ammonia etching, the well-defined Ag3PO4 dodecahedrons changed to hollow polyhedrons with increasing etchant dosage. From the XRD, TEM, DRS and XPS results, it could be inferred that ammonia etching of Ag3PO4 led to an obvious lattice shift and significantly narrowed band gap energies due to the formation of Ag vacancies and metallic Ag. These microstructural variations notably affected the photocatalytic performance of Ag3PO4 photocatalysts. The activity of the etched samples was found to be significantly enhanced toward the degradation of methyl orange (MO) dye under visible light irradiation. The highest activity was observed over the sample etched by 0.15 M ammonia solution, which exceeded that of bare Ag3PO4 by a factor of about 6.2 times. The reasons for the improvement of photocatalytic performance of etched samples may be that the newly formed Ag vacancies and metallic Ag improved the separation efficiency of photogenerated electrons and holes. (C) 2016 Elsevier B.V. All rights reserved.