Abstract Tungsten oxide (WO3) nanoparticles doped with different amounts of manganese ions (W1−xMnxO3, where x = 0.011, 0.022 and 0.044) were synthesised by hydraulic acid-assisted precipitation, followed by thermal calcinations. The powders were characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and magnetic measurements. The monoclinic structure at room temperature (∼293 K) found for un-doped WO3 was preserved even with Mn doping. However, doping with Mn ions caused decease in unit-cell volume and slight increase in crystallite size (CS) of host WO3. The hydrogenation was observed to corrode the crystallites without changing in crystalline structure. Controllable room-temperature ferromagnetic (RT-FM) properties were obviously observed with hydrogenated WO3 doped with Mn. In addition, there existed an optimum doping concentration of Mn in WO3 to obtain superior FM properties. Therefore, Mn-doped WO3 nanopowders, owning to these amazingly tunable magnetic properties, could be considered a potential candidate for many applications partially required FM properties such as optical phosphors and catalysts. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.