An efficient method for the synthesis of title compounds viz., 3-(3-phenyl-7H-1,2,4]triazole[3,4][1,3,4]thiadiazin-6- yl)-chromen-2-ones (3) has been reported by the condensation of 3-(2-bromoacetyl)chromen-2-ones (1) with 4- amino-5-phenyl-4H[1,2,4]triazole-3-thiols (2). The reaction has been carried out under conventional as well as under microwave irradiation conditions. The latter procedure has been found to be much more efficient in terms of reaction time and yield. The structures of all the compounds have been established on the basis of their spectral and analytical data.