In the present study, a series of S-[5-(phenylamino)-1,3,4-thiadiazole-2-yl] benzenecarbothioate and S-[5-(phenyl amino)- 1,3,4-thiadiazole-2-yl] ethanethioate were prepared by refluxing benzoyl chloride and acetyl chloride in presence of potassium carbonate with 5-(phenyl amino)-1,3,4-thiadiazole-2-thiol. 5-(Phenyl amino)-1, 3, 4-thiadiazole-2-thiol were prepared by cyclization of arylthiosemicarbazide with carbondisulphide. The structure of new compounds prepared during present investigation have been authentically established by their IR, 1H NMR and Mass spectral studies. The antibacterial and antifungal activities of thiadiazole derivatives also reported. Some of these derivatives exhibit significant antimicrobial activity. Key words: thiadiazole, thiosemicarbazide, antibacterial, antifungal.