In this study, a novel magnetically heterogeneous catalyst based on the immobilization of boron sulfonic acid onto Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂–BSA) is reported. Fe₃O₄@SiO₂–BSA was characterized via FT-IR, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM) analysis. The performance ability of this catalyst including acid sites was evaluated for the synthesis of pyrano coumarins under solvent-free conditions with high yields. Thermal stability of the catalyst and its easy separation by a magnetic field make this catalyst a good heterogeneous system and a useful alternative to other heterogeneous catalysts.