The title compounds, 2-substituted phenyl-3-{1-cyclopropyl-6-fluoro-7-[4-(2,3-dichlorophenylpiperazin-1-yl]-4-oxo-1,4-dihydroquinoline} carboxamido-1,3-thiazolidin-4-ones 6a-j, have been synthesized after several structural variations viz. hydrazide 2 via acid chloride, Schiff base formation and cyclization of Schiff base followed by condensation with N-(2,3-dichlorophenyl)piperazine from the lead molecule 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinolin-3-carboxylic acid 1. The synthesized compounds were tested for their antibacterial and antifungal activity (MIC) in vitro against organisms viz. S. aureus, S. pyogenes, E. coli, P. aeruginosa, C. albicans, A. niger and A. clavatus taking gentamycin, ampicillin, chloramphenicol, ciprofloxacin, norfloxacin, nystatin and greseofulvin as standard drugs. Compounds 4i, 5i and 6j (2-Cl, 2-Cl and 4-Cl) demonstrated excellent activity compared with ampicillin.