A multifunctional Ag-ZnO/g-C3N4 composite was hydrothermally synthesized using aqueous dispersion of g-C3N4 particles with Ag and ZnO precursors by heat treatment at 130°C for 3h. The prepared composite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and photoluminescence spectroscopy (PL) to reveal the formation of composite metal, metal oxide, and carbon nitride. Well attached ZnO microflowers were formed on the surface of g-C3N4 sheets, when hydrothermal solution was treated without silver precursor. However, silver doped ZnO nanoflowers were appeared on g-C3N4 sheets, when the silver nitrate containing hydrothermal solution was treated. The photocatalytic activity and antibacterial properties of as-prepared composite were studied by photocatalytic reduction of methylene blue (MB) solution and destruction of Gram-negative Escherichia coli bacteria, respectively. It was found that Ag-ZnO/g-C3N4 composite exhibited better photocatalytic and antibacterial activity compared to g-C3N4 and ZnO/g-C3N4 particles. A sample of Ag-ZnO/g-C3N4 also exhibited favorable stability and durability. The nanocomposite obtained from this simple and convenient facile one-pot synthesis may become a prospective photocatalyst.