Ultrathin Ag2Mo3O10 center dot 2H(2)O nanowires (NWs) were synthesized by soft chemistry under atmospheric pressure from a hybrid organic inorganic polyoxometalate (CH3NH3)(2) [Mo7O22] and characterized by powder X-ray diffraction, DSC/TGA analyses, FT-IR and FT-Raman spectroscopies, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Their diameters are a few tens of nanometers and hence much thinner than that found for silver molybdates commonly obtained under hydrothermal conditions. The optical properties of Ag2Mo3O10 center dot 2H(2)O NWs before and after UV irradiation were investigated by UV-vis-NIR diffuse reflectance spectroscopy revealing, in addition to photoreduction of Mo6+ to Mo5+ cations, in situ photogeneration of well silver Ag-0 nanoparticles on the surface of the NWs. The resulting Ag@Ag2Mo3O10 center dot 2H(2)O heterostructure was confirmed by electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), and Auger spectroscopy. Concomitant reduction of Mo6+ and Ag+ cations under UV excitation was discussed on the basis of electronic band structure calculations The Ag@Ag2Mo3O10 center dot 2H(2)O nanocomposite is an efficient visible-light-driven plasmonic photocatalyst for degradation of Rhodamine B dye in aqueous solution.