Herein, using the hydrothermal route, In(OH)3 nanostructures were synthesized by the reaction of In(NO3)3·5H2O, ethylenediamine, and hydrazine hydrate. According to SEM results, ethylenediamine and hydrazine can control the particle growth and play an important role in formation of Indium hydroxide nanostructures. The morphology and microstructure of the obtained products were characterized by X-ray diffraction patterns, energy-dispersive X-ray spectroscopy, fourier transformed infrared spectrum, UV–visible spectrum and scanning electron microscopy. Furthermore, by calcinating In(OH)3 at 400 °C for 2 h in air, In2O3 nanoparticles were prepared. Then, the efficiency of In2O3 nanoparticles as a photocatalyst for the decolorization of methylene blue using visible light irradiation has been evaluated .