Graphene oxide (GO) sheets with a low concentration (similar to 1 wt%) were deposited on surface of hydrothermally synthesized ZnO nanorod films. The deposited films were heat treated at 450 degrees C in order to achieve suitable GO/ZnO hybrid thin films for photocatalytic purposes. The photocatalytic activity of the nanocomposite films was investigated based on degradation of methylene blue (MB) dye which is a typical pollutant model. The GO/ZnO hybrid thin films could degrade higher MB (similar to 90%) than the bare ZnO nanorods (which showed only similar to 75% degradation) after 450 min UV irradiation. A further significant improvement (resulting in a nearly complete degradation of MB) was achieved by exposing the GO/ZnO films to UV irradiation. The improvement was assigned to UV-assisted photocatalytic reduction of GO sheets and separation of photoexcited electron-hole pairs of ZnO by the UV-treated GO sheets. These results highlight application of UV treatment in improving the photocatalytic activity of GO-containing ZnO nanostructures. (C) 2016 Elsevier B.V. All rights reserved.