Urea was successfully immobilized on the surface of chloropropyl‐modified Fe 3 O 4 @SiO 2 core–shell magnetic nanoparticles, then supported by MgBr 2 and acts as a unique catalyst for oxidation of benzylic alcohols to aldehydes and ketones, and ortho ‐formylation of phenols to salicylaldehydes. The prepared catalyst was characterized by FT‐IR, transmission electron microscopy, scanning electron microscopy, X‐ray powder diffraction, dispersive X‐ray spectroscopy, CHN and TGA. It was found that Fe 3 O 4 @SiO 2 ~ urea/MgBr 2 showed higher catalytic activity than homogenous MgBr 2 , and could be reused several times without significant loss of activity.