H-ZSM5 is applied as an efficient, highly reusable, and heterogeneous catalyst for the oxidation of sulfides to sulfoxides using 30% H₂O₂ under solvent-free conditions at room temperature. A variety of aromatic and aliphatic sulfides with different functional groups were successfully oxidized with good to excellent yields in short reaction times. The catalyst can be easily recovered by simple filtration and recycled for several consecutive runs without any significant loss of its catalytic activity.