3,4-Dihydropyrimidin-2(1H)-one derivatives were synthesized by Biginelli reaction under microwave irradiation using oxalic acid as a new, efficient, and environmentally benign catalyst. Antioxidant properties of synthesized compounds were evaluated by three methods, viz., radical scavenging effect on 2,2-diphenyl-1-picrylhydrazyl radicals, reducing power and Fe2? chelating activities. The compounds having –OH group on benzene ring were found to have higher activity. Amongst the 12 synthesized compounds, four were found to have significant antioxidant activity.