This work is reported on the synthesis of Fe3O4/eggshell nanocomposites in the absence of any stabilizer or surfactant. Fe3O4 magnetic nanoparticles were established on the egg shell nano-composite. The nanocompositeshave shown high catalytic activities in the synthesis of Tetrahydrobenzo[b]pyran. These derivatives were synthesized via an one‐pot three‐component condensation of aromatic aldehydes with malononitrile and dimedonewith excellent yields in the presence of Fe3O4/eggshell nanocomposites as a highly efficient heterogeneous catalyst. The obtained catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD) and Vibrating sample magnetometer (VSM). The developed technique of nano-composite synthesis is energy efficient since the reactions carried out in single step. The present catalyst is possible to be used for the production of biodiesel.