Present study demonstrates the synthesis of alumina nanoparticles (NPs) by sol-gel method and characterized by various standard microscopic techniques like Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Energy Dispersive Spectroscopy (EDS), FT-IR, UV-visible, and Thermogravimetry-Differential Thermogravimetry (TG-DTA) to evaluate the size, shape and composition of nanoparticles. Furthermore, a solvent free green synthesis of 3, 4-dihydropyrimidinones derivatives were carried by using alumina nanoparticles (γ-Al2O3 NPs) as a catalyst through Biginelli reaction of aromatic aldehydes, β-ketoesters, and urea. The structures of the obtained products were confirmed by Fourier transform infrared (FT-IR), and proton nuclear magnetic resonance ( 1 H NMR) spectra. Effective results were obtained by using nano catalyst. Therefore, present protocol is favored as it offers advantages of higher productivity, short reaction times, simplicity and easy workup. Besides, catalyst is an inexpensive, reusable and recyclable up to four cycles without loss of its activity.