Ag/AgBr-grafted graphite-like carbon nitride (g-C3N4) is fabricated by the in situ photoreduction of AgBr/g-C3N4 hybrids prepared by a deposition–precipitation method. The Ag/AgBr/g-C3N4 hybrids exhibit a strong absorbance in the visible and near-IR region because of the surface plasmon resonance absorption of Ag nanocrystals. Compared with bare g-C3N4 and Ag/AgBr nanoparticles, a 28-fold and six-fold enhancement in the degradation rate of rhodamine B is observed over Ag/AgBr/g-C3N4 hybrids under visible-light irradiation, respectively. The immense enhancement of the photocatalytic activity is attributed to the extended absorption in the visible-light region, effective charge separation, and synergistic enhancement in the ternary Ag/AgBr/g-C3N4 system. Moreover, the composite can be reclaimed easily by sedimentation without any decrease of its photocatalytic activity. This study provides new insight into the fabrication of highly efficient and stable g-C3N4-based plasmonic photocatalysts and facilitates their practical application to solve environmental issues.