Visible-light responsive plasmonic Ag2O/Ag/g-C3N4 nanosheets (NS) were successfully prepared by a simple and green photodeposition method. The obtained composites were characterized by XRD, Fourier transform infrared, transmission electron microscopy, UV-vis, and the photoluminescence (PL) results indicated that the Ag2O/Ag/g-C3N4 NS composites showed better photoabsorption performance than g-C3N4 due to the surface plasmon resonance effect of Ag nanoparticles. Meanwhile, the composite exhibited excellent photocatalytic activities, which was ∼3.8 and ∼3.0 times higher than those of bulk g-C3N4 and pure g-C3N4 NS, respectively. Moreover, the as-prepared composites showed a high structural stability in the photodegradation of Rhodamine B. A possible photocatalytic and charge separation mechanism was suggested based on the PL spectra and the active species trapping experiment.