In the present study diselenide stabilized on silica coated FeO magnetic nano particles asa novel, highly efficient and magnetically retrievable heterogeneous catalyst was designed, synthesized and introduced. Full characterization of the newly prepared magnetic nanocatalyst was authenticated using several physico-chemical characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction patterns (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Thereafter, the catalytic performance of this (FeO@SiO-Se) nanocatalyst was investigated in oxidation of aldehydes using HO as the clean oxidant under aqueous conditions. Under the title conditions, a range of both aromatic and aliphatic aldehydes can be converted into the corresponding carboxylic acid products with excellent yields. Additionally, the magnetic nanoparticles could be conveniently recovered using an external magnetic field and reused four times without discernible decrease of efficiency. Some of the other outstanding features of this methodology are short reaction times, simple and easy work-up procedure, eco-friendly nature and cost effectiveness that make it economic, sustainable and in agreement with some green chemistry protocols.