Magnetite nanoparticles coated with mesoporous silica, Fe₃O₄@SiO₂, were prepared. Surface functionalization of this core–shell nanocomposite with (3-aminopropyl)trimethoxysilane (APTMS) followed by its reaction with Cu(OAc)₂ was used to develop a new heterogeneous copper complex (Fe₃O₄@SiO₂–APTMS–Cu). The structure and composition of the synthesized nanocatalyst were characterized by FTIR, SEM, VSM, TEM, XRD, and ICP analyses. The catalytic activity of the synthesized catalyst was probed in the oxidative amidation reaction of methyl arenes with amine hydrochloride salts. Various primary, secondary, and tertiary amides were prepared by this method. The magnetic properties of this catalyst lead to easy separation as well as providing significant catalyst recyclability. The catalyst is reusable 6 times without significant decrease in its catalytic activity.