An efficient, one-pot synthesis of 3-substituted-4 H-[1,2,3]triazolo[5,1- c][1,4]oxazin-6(7 H)-ones is developed via sequential esterification, substitution, and 1,3-dipolar cycloaddition processes of various propargyl alcohols, chloroacetyl chloride, and sodium azide. This method provides a variety of novel 1,2,3-triazole-fused oxazinones and has several advantages including simple operation, high efficiency, and good-to-excellent product yields (80%–95%) without the need to isolate the ester and azide intermediates.