A series of 5-substituted 1H-tetrazoles were synthesized in DMF by the [3 + 2] cycloaddition reaction under the effect of microwave irradiation (10–30 min, fixed mode, 90 °C, 140 W) in the presence of highly efficient superior catalyst. For this reaction, different aromatic nitriles with the sodium azide were used and superior monodisperse (Md) platinum nanoparticles (Pt NPs) decorated on activated carbon (AC) served as a catalyst. Md-Pt NPs@AC were reproducibly and easily produced by double solvent reduction of PtCl₄ in room temperature and characterized by transmission electron microscopy (TEM), the high resolution electron micrograph (HRTEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The sum of their results shows the formation of highly crystalline and colloidally stable Md-Pt NPs@AC. The catalytic performance of these new NPs were investigated for the synthesis of 5-substituted 1H-tetrazoles, in which they were found to be exceptional reusable, isolable, stable and highly efficient heterogeneous catalyst. All prepared tetrazole products were obtained with perfect yield by using current heterogeneous catalyst and characterized by melting points, FT-IR, ¹H-NMR, ¹³C-NMR and HRMS analyzes.