Facile synthesis of novel rGO-supported AgI decorated TiO2 mesocrystals (AgI-TMCs-rGO) and their photocatalytic activity under visible light irradiation are reported. The catalysts were prepared by combining the hydrothermal reaction process and in situ deposition-precipitation method. The structural features and chemical compositions of the prepared catalysts were investigated by HRTEM (high resolution transmission electron microscopy), XRD (x-ray powder diffraction), Raman spectra, XPS (x-ray photoelectron spectroscopy), UV-vis DRS (UV-vis diffuse reflectance spectra), PLS (photoluminescence spectra), and N2 physisorption measurements. The AgI-TMCs-rGO catalysts featured a large surface area, high adsorption capacity, enhanced photo-induced charge separation and strong absorbance of visible light. The intimate contact of various components and the fast transfer of charge carriers effectively suppresses photolysis of AgI and favors the structural stability of AgI-TMCs-rGO. The photocatalytic activity of the catalysts was evaluated by degrading Rhodamine B (RhB) in an aqueous solution under visible light irradiation. The highest photocatalytic activity was observed in the sample 20%Ag-TMCs-rGO, attributed to the synergistic effects of a lower band gap and a lowerrecombination rate of the charge carriers, along with the larger surface area of the fabricated sample.