5-Mercapto-4-Amino-3-(3-Pyridyl)-1,2,4-Triazole (4) is prepared by condensing Potassium- 3-(3-Pyridyl) Dithiocarbazinate (3) with hydrazine hydrate. Compound (4) upon condensation with aromatic acids/aryloxyacetic acids in presence of POCl3 will yields the title compounds 1,2,4-Triazolo [3,4-b]1,3,4-Thiadiazoles (5a-m). The newly synthesized compounds were assigned on the basis of IR, 1H-NMR & MASS spectral data. The compounds 5a-m were evaluated for their In-Vitro antibacterial and antifungal activities. Some of the new compounds showed good activity against some bacterial organisms.