Nanoparticles of zinc oxide (ZnO) sensitized with silver iodide (AgI) were synthesized by a chemical precipitation method and were found to be a visible light driven photocatalyst. The characterization of prepared photocatalyst was studied using UV-visible diffuse reflectance spectroscopy (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Average crystallite size determined by XRD was 21.56 nm for ZnO and 23.44 nm for AgI sensitized ZnO (AgI-ZnO). The photocatalytic efficiency of AgI-ZnO was evaluated by the decolorization of rosaniline hydrochloride dye (RA) under visible light irradiation. The influence of various operational parameters such as the effect of pH, catalyst dosage and initial dye concentration on the photodecolorization was investigated in detail. The removal percentage of chemical oxygen demand (COD) and total organic carbon (TOC) was determined to evaluate the mineralization of RA during photodecolorization. Maximum decolorization, COD removal and total organic carbon (TOC) reduction were 88%, 75% and 68% respectively, under the optimum conditions. (C) 2012 Elsevier B.V. All rights reserved.