Ag3PO4 has been proven to be a promising catalyst with superior activity compared to other existing visible-light-driven photocatalysts. In this work, Ag3PO4 nanoparticles were deposited on the surface of two-dimensional Ag2S sheets by an in situ synthesis strategy. The microstructure, composition, and performance of the resulting Ag3PO4/Ag2S composites could be tailored by surface-functioned Ag2S sheets. The composite reached optimum performance when the molar ratio of Ag2S to Ag3PO4 was 0.31, showing a 2-fold enhancement in the degradation rate in comparison to pure Ag3PO4. Efficient separation of photogenerated electron-hole pairs was achieved through a Z-scheme system in which Ag particles served as the center for the combination of electrons at the conduction band of Ag3PO4 and holes at the valence band of Ag2S. In addition to the matched band structure of Ag2S and Ag3PO4, the monodispersed Ag3PO4 nanoparticles were efficient in light harvesting due to the presence of Ag2S. The advantageous interface effect produced by Ag2S sheets and nano-sized Ag3PO4 nanoparticles also contributed to the improvement in photocatalytic activity.