Novel protocol towards multifunctional magnetic organic–inorganic core–shell nanostructured catalysts of Fe₃O₄@SN/HPW@CG–Ag with tailored properties are presented in this work. Such nanocomposites congregate the properties and functions of a single component into a whole. For instance, Fe₃O₄ cores protected by amino-functionalized SiO₂ shell endowed the composites with superparamagnetism (28.6 emu g⁻¹) and thereby facilitate the process of separation and recovery. Phosphotungstic acid, as a bridging agent, provided a strong interaction for the anchoring of glutaraldehyde cross-linked chitosan onto the surface of Fe₃O₄@SN. More interestingly, chitosan could simultaneously behave as a stabilizer and reductant for the in situ synthesis of “green” Ag NPs without addition of any other reducing agent or organic solvent, and Ag NPs provided the compounds with a catalytic performance. Further the size, loading of Ag NPs and the thickness of the chitosan layer were all controllable. Meaningfully, the as-synthesized catalyst Fe₃O₄@SN/HPW@CG–Ag exhibited an exceptional catalytic performance for the reduction of 4-nitrophenol in the presence of sodium borohydride (the reaction was accomplished within 7 min) and could be reused at least 10 times with good stability by means of convenient magnetic separation. Thence, the design philosophy of the multifunctional robust Ag-based nanocatalysts may pave the way for the synthesis of other catalyst systems with long-term stability.