Herein, we report the ease synthesis of mesoporous WO3-TiO2 nanocomposites at different WO3 contents (0-5 wt%) together with their photocatalytic performance for the degradation of the imazapyr herbicide under visible light and UV illumination. XRD and Raman spectra indicated that the highly crystalline anatase TiO2 phase and monoclinic and triclinic of WO3 were formed. The mesoporous TiO2 exhibits large pore volumes of 0.267 cm(3)g(-1) and high surface areas of 180 m(2) g(-1) but they become reduced to 0.221 cm(3)g(-1) and 113 m(2) g(-1), respectively upon WO3 incorporation, with tunable mesopore diameter in the range of 5-6.5 nm. TEM images show WO3-TiO2 nanocomposites are quite uniform with 10-15 nm of TiO2 and 5-10nm of WO3 sizes. Under UV illumination, the overall photocatalytic efficiency of the 3% WO3-TiO2 nanocomposite is 3.5 and 6.6 times higher than that of mesoporous TiO2 and commercial UV-100 photocatalyst, respectively. The 3% WO3-TiO2 nanocomposite is considered to be the optimum photocatalyst which is able to degrade completely (100% conversion) of imazapyr herbicide along 120 min with high photonic efficiency 8%. While under visible light illumination, the 0.5% WO3-TiO2 nanocomposite is the optimum photocatalyst which achieves 46% photocatalytic efficiency. (C) 2015 Elsevier B.V. All rights reserved.