<p>Herein, chitosan-supported molybdenum Schiff base complex was conveniently synthesized by using a post-modification method. The obtained biocomposite was fully analyzed by a variety of diverse physicochemical ways including FT-IR, EDX, XPS, XRD, TGA, ICP-OES, and SEM. Afterwards, it was used as a heterogeneous catalyst for the oxidation of sulfides to sulfoxides. The influences of various reaction parameters on the catalytic performance of the synthesized catalyst were explored in detail. The catalyst demonstrated excellent catalytic activity and chemoselectivity for the oxidation of various sulfides to the corresponding sulfoxides by H₂O₂ as a green oxidant in water at 50&#xa0;°C. Notably, the catalyst could be removed simply from the reaction mixture and recycled for at least seven recycling reactions with only a minor loss of activity. The use of chitosan as catalyst support, green and mild reaction conditions, high chemoselectivity, and reusability of the catalyst are the key merits of the catalytic system.</p>