The aim of this article is to prepare Tungsten oxide (WO3) nanoparticle along with manganese (3 and 10 wt%) by Microwave irradiation method. The physical properties of the synthesized Mn doped WO3 materials were characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), transmission electron microscope (TEM), UV-diffuse reflectance spectroscopy and photoluminescence studies. Powder XRD results reveal that the Mn doped WO3 crystallizes in monoclinic structure. FTIR spectroscopy analysis reveals the presence of tungsten and oxygen in the synthesised material. TEM micrograph illustrate that both pristine and Mn doped WO3 nanopaticles are having spherical shaped morphology with average particle size from 35-50 nm. A significant red shift in the absorption edge and decrease the band gap energy for WO3 nanoparticles were confirmed with UV-DRS spectra analysis. The defects and oxygen deficiencies were analysed by photoluminescence spectroscopy. The photocatalytic activites of the pure and Mn doped WO3 samples were evaluated by the degradation of methylene blue in a aqueous solution under visible light irradiation. The photocatalytic activity for Mn doped WO3 was much higher than that of the pure WO3.