A novel series of 2-(3, 5-dimethyl-1-phenyl-1H-4-pyrazolyl)-3-(aryl/heteroaryl)-1, 3-thiazolidin-4-one derivatives 4a-h has been synthesized readily in one-pot from 3, 5-dimethyl-1-phenyl-1H-4-pyrazolecarbaldehyde (3), and characterized via IR, NMR, MS and elemental analyses. Further, these compounds were screened for antibacterial (MIC) activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Staphylococcus pyogenes. Amongst them, compounds containing pyridyl 4g and pyrimidinyl 4h moiety exerted superior antibacterial activity against S. aureus and E. coli at the concentration of 6.25 µg/mL, which is less than the concentration of the standards neomycin and streptomycin, and emerged as potential molecules for further development.