Several new N-[(4-oxo-2-substituted aryl-1, 3-thiazolidine)-acetamidyl]-5-nitroindazoles (4a-l) were synthesized from N-(arylidene amino acetamidyl)-5-nitroindazoles (3a-l). The reactions were carried out by both conventional as well as microwave method. The structures of these compounds were confirmed by IR, (1)H NMR, (13)C NMR, FAB-mass spectra and also by microanalytical data. The newly synthesized compounds were evaluated for their antimicrobial activity against variety of bacterial and fungal strains. The compounds 4 g and 4 h showed the maximum antibacterial activity (MIC 11 and 10 microg/mL) against Escherichia coli and antifungal activity (MIC 9 and 8 microg/mL) against Fusarium oxysporum.