Ternary Ag2O/TiO2/nanographene platelet (Ag2O/TiO2/NGP) composites containing various amounts of NGP were synthesized using a microwave-assisted method and were used as catalysts for degradation of organic dyes in aqueous solution. The composites were characterized by various methods, and their photocatalytic performance was systematically investigated with respect to degradation of methylene blue. Compared with pure TiO2 and Ag2O nanoparticles as well as Ag2O/TiO2 composites, the Ag2O/TiO2/NGP composites exhibited superior photocatalytic performance in the UV and visible light range. The results also indicated that Ag2O/TiO2/NGP composites could be used as efficient broad-spectrum catalysts for the removal of several dye contaminants in aqueous solutions. The correlation between photocatalytic mechanism and physical properties of the catalysts was discussed. The effects of the addition of hydrogen peroxide (H2O2) and persulfate on MB degradation were also investigated. Photocatalytic efficiency was noticeable in the presence of both oxidizers. Because inorganic anions are common substances in natural water, their influence was also evaluated. They were found to inhibit the catalytic activity of Ag2O/TiO2/NGP composites. Their effectiveness in inhibiting photocatalytic degradation of MB was CO32- > NO3- > HPO4- > Cl- > SO42-.