2-[(2,6-Dichlorophenyl)amino]phenylacetic acid (A) on reaction with thionyl chloride gave corresponding acid chloride (B). A series of (4-oxo-thiazolidinyl)sulfonamides of quinazolin-4(3H)ones (4a-l) were prepared from Schiff bases (3a-l) of 2-[2-(2,6-dichlorophenyl)amino]phenylmethyl-3-[(4-aminophenyl)sulfonamido-1-yl]quinazolin-4(3H)one (D) and substituted aromatic aldehyde. Newly synthesized compounds have been examined on the basis of elemental analysis, IR, 1H NMR and 13C NMR spectra. Antibacterial activity (minimum inhibitory concentration - MIC) against Gram-positive (S. aureus & S. pyogeneus) and Gram-negative (P. aeruginosa and E. coli) bacteria, as well as antifungal acivities (MIC) against C. albicans, A. niger and A. clavatus were determined by broth dilution method. Some of the compounds were endowed with a remarkable antibacterial as well as antifungal acivities.