In this study, magnetic polyborate nanoparticles (MPBNPs) were prepared via a simple procedure from boric acid by using ball-milling and then characterized by various spectroscopic, microscopic and analytical methods including FT-IR, EDX, XRD, FESEM, VSM and TGA analysis. The obtained MPBNPs were further explored, as a green and highly efficient catalyst, in the multi-component synthesis of a wide range of tetra-substituted imidazoles from cascade cyclocondensation as well as in situ air oxidation of benzil or benzoin, aromatic aldehydes, primary amine and ammonium acetate in EtOH, as a green solvent, under reflux conditions. Additionally, environmentally friendly conditions for the preparation of the catalyst by the use of non-toxic reactants, facile procedure and high to excellent yields of the desired products as well as the use of a green solvent are some advantages of this new protocol.