Imidazole tribromide immobilized on magnetic nanoparticles as a bromine source was prepared and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) techniques. The high catalytic activity of this novel catalyst was investigated in the oxidation of sulfides to sulfoxides using aqueous hydrogen peroxide as an oxidant at room temperature under solvent-free conditions. More importantly, the catalyst could be easily recovered by an external magnet and reused five times without any significant loss of catalytic activity.