For the first time scandium triflate was supported on modified Fe3O4 magnetic nanoparticles [MNPs-PhSO3-Sc(OTf)2] and characterized using scanning electron microscopy (SEM), inductively coupled plasma analysis (ICP), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM) techniques. The MNPs-PhSO3-Sc(OTf)2 was applied as a magnetically recyclable heterogeneous Lewis acid nanocatalyst for the selective oxidation of a variety of sulfides to sulfoxides using hydrogen peroxide as a green oxidant resulting in 90–98% yields under solvent-free conditions at room temperature. It could also be recovered and reused for at least 15 reaction cycles without considerable loss of activity.