Mesoporous In2O3-TiO2 nanocomposites were successfully synthesized through sol gel approach in the presence of a suitable template. Their photonic efficiencies have been determined by measuring photooxidation of the herbicide imazapyr and compared with those of porous TiO(2 )and of the commercial photocatalyst Hombikat UV-100. The X-ray diffraction patterns indicated the formation of tetragonal anatase and rutile phases of TiO2. The highest photonic efficiency values of 13.5% were obtained for the 0.1% In2O3-TiO2 nanocomposite in comparison with a value of 12% for mesoporous TiO2 and of 10.8% for commercial UV-100. As a result of the synergetic effect of TiO2 (anatase & rutile) and In2O3 nanoparticles, it is suggested that heterostructured In2O3-TiO2 nanocomposites are formed and are promoting the separation of photogenerated charge carriers. Moreover, the In2O-TiO2 nanocomposites could be easily reused up to 5 times with only a slight decrease in their photocatalytic activity. The design for merging unique In2O3 nanoparticles with a mesoporous TiO2 network can be regarded as an innovation to further promote the photocatalytic properties of the latter.