Titanium dioxide/zinc oxide/chitosan nanocomposite thin films (TiO₂/ZnO/chitosan NTFs) were prepared by entrapping zinc ions and nanosized TiO₂ in chitosan thin films under mild conditions. The structure, thermal property, and surface morphology of TiO₂/ZnO/chitosan NTFs were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The photocatalytic activity of TiO₂/ZnO/chitosan NTFs was evaluated by photocatalytic decolorization of methyl orange in aqueous solution as a model pollutant under simulated solar irradiation. The HRTEM results revealed that well-dispersed and uniform TiO₂/ZnO nanocomposite with diameters of 5–15nm were embedded in chitosan films. The TiO₂/ZnO/chitosan NTFs exhibited high photocatalytic activity under simulated solar irradiation. After 4h of irradiation by simulated solar light, over 97% of methyl orange solution (15mgL⁻¹) was decolorized with 0.5gL⁻¹ of the photocatalyst. The TiO₂/ZnO/chitosan NTFs could be reused, which meant that the adsorption-photocatalytic decolorization process could be operated at a relatively low cost. Since this process does not require the addition of hydrogen peroxide and uses solar light, it can be developed as an economically feasible and environmentally friendly method to decolorize or treat dye wastewater using sunlight.