In this paper, we discuss the synthesis and characterization of pure and silver (Ag) doped tungsten oxide nanoparticles prepared by microwave irradiation method. The size and morphology were studied by powder X-ray diffraction and the results reveal that the pure and Ag (3 and 10 wt%) doped WO3 crystallizes in monoclinic structure. TEM analysis shows both pristine and silver doped WO3 nanoparticles were spherical morphology with a average size from 30 to 40 nm. Scanning electron microscopy result indicates spherical shaped morphology with an average diameter of 40-30 nm, which is in proper agreement with the average crystallite sizes calculated by Scherrer's formula. A considerable red shift in the absorbing band edge and decrease the band gap energy from 3.00 to 2.85 eV for Ag doped samples were observed by using UV-DRS spectra analysis. The defects in crystal and oxygen deficiencies were analyzed by photoluminescence studies. The photocatalytic activities of the pure and Ag doped WO3 samples were evaluated by the degradation of methylene blue in an aqueous solution under visible light irradiation. The photocatalytic activity for Ag doped WO3 was much higher than pure WO3.