In this paper, a novel, cost-effective, and green methodology has been investigated for preparation of cobalt (II) nanoparticles supported on the nanodiamond carbon structure-grafted-polyethyleneimine@folic acid (ND-g-PEI@FA@Co(II)) nanocomposite. Some of the physicochemical characteristics of the synthesized efficient heterogeneous nanocatalyst, including bond formation and functional groups, percentage of elements, crystalline phase, and surface morphology were studied using techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Field emission scanning electron microscopy (FE-SEM). Following the principles of green chemistry, this nanocatalyst has been used in the production of 5-substituted 1H-tetrazole derivatives using different benzaldehyde derivatives, sodium azide and malononitrile agents in ethanol eco-friendly solvent with high efficiency. The mechanism of tetrazole synthesis is carried out through cascade condensations, such as knoevenagel condensation, 1,3-dipolar cycloaddition, and tautomerization reactions. The main advantages of ND-g-PEI@FA@Co(II) nanocatalyst include facil preparation, easy separation, low consumption of catalyst for this multi-component reaction (MCR), use of cheap and recyclable materials, excellent product yield, and reusability up to 4 times with good efficiency. The substrate used in this heterogeneous catalyst (ND) with appropriate thermal stability, abundant availability in large quantities, non-toxicity are prominent features of the synthesized nanocomposite.