Some new 5-methoxy/ethoxy-2,3-[2'-(3''-chloro-2''-oxo-4''-substituted-aryl-1''-azetidinyl)-1',3',4'-thiadiazino]indoles 13-20 and 5-methoxy/ethoxy-2,3-[2'-(2''-substituted-aryl-4''-oxo-1'',3''-thiazolidin-3''-yl)-1',3',4'-thiadiazino]indoles 21-28 have been synthesized from 5-methoxy/ethoxy-2,3-[2'-(substituted-benzylidinylimino)-1',3',4'-thiadiazino]indoles 5-12. These newly synthesized compounds were characterized by elemental and spectral analysis. Further, compounds 5-28 of the present series have been screened for their antibacterial and antifungal activities. Both minimal inhibitory concentration (MIC) and inhibition zones were determined in order to monitor the efficacy of the synthesized compounds. Compounds 14 and 16 were found to be the most potent members of the present series, they showed maximal antibacterial and antifungal properties much better than the standard drugs.