In recent years, tuning the structural and photocatalytic properties of semiconductors with the introduction of Ag nanoparticles through their well-known surface plasmon resonance (SPR) effect has gained much interest in the field of environmental applications. Herein, a new plasmonic Ag/AgBr/Cs2Nb4O11 composite was successfully fabricated by applying a visible-light reduction method using the pre-prepared AgBr/Cs2Nb4O11 and Cs2Nb4O11 catalysts synthesized by sonication-assisted deposition precipitation and solid-state methods, respectively. The synthesized samples were characterized by FESEM/EDX/EDS elemental mapping, TEM/HRTEM, XRD, N-2-sorption, UV-Vis DRS, PL and XPS techniques. Photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation was performed for the composite and well compared with the counter parts. In contrast to parent Cs2Nb4O11, the AgBr/Cs2Nb4O11 and Ag/AgBr/Cs2Nb4O11 composites exhibited extended absorption edges and improved photoabsorption in the visible region, which are discretely due to the intrinsic absorption of AgBr and SPR effect of metallic Ag nanoparticles. The PL results revealed that the ternary composite showed a better separation of photo-generated charge carriers. Amongst the samples, the Ag/AgBr/Cs2Nb4O11 composite exhibited the highest photoactivity, degrading 97% of RhB after 60min of visible-light irradiation. The correlation between the structural properties and the origin of the enhanced photocatalytic activity of the Ag/AgBr/Cs2Nb4O11 composite is discussed in detail, and possible reaction mechanism is proposed. Moreover, the good recycling ability (up to 5 cycles) suggests that the Ag/AgBr/Cs2Nb4O11 composite can be exploited successfully in the wastewater treatment. [GRAPHICS] .