The series of new Triazolo[3,4-b][1,3,4]thiadiazole (7a-e) and Triazolo[3,4-b][1,3,4]thiadiazine (8a-e) derivatives of chromeno[4,3-b]pyridin-5-one were successfully synthesized by multistep synthesis of 4-amino-3-Formyl-2-oxo- 2H-chromene. The newly synthesized compounds were well characterized by IR, 1HNMR, 13CNMR, Mass and Elemental analysis. The compounds were evaluated for their antimicrobial activity against three antibacterial species namely Staphylococcus aureus, Escherichia coli and Bacillus cereus and two fungal species namely Candida albicans and Aspergillus clavatus. Most of the compounds show very good antimicrobial inhibition while compared with the standard drug such as Ciprofloxacin and Ketoconazole.