A series of 2-(5-chlorobenzo[d]thiazol-2-ylimino)-5-((3-(p-substituted phenyl)-1-phenyl-1H-pyrazol-4-yl)methylene)thiazolidin-4-ones (3a–h) were prepared from 2-(5-chlorobenzo[d]thiazol-2-ylimino)thiazolidin-4-one (1) and 1-phenyl-3-(p-substituted phenyl)-1H-pyrazole-4-carbaldehyde (2a–h). All compounds were characterized using elemental analytical (C, H, and N) and spectral (FT-IR, 1H NMR, 13C NMR and GC–MS) data. These compounds were screened for their antibacterial, antifungal and antimycobacterial activities. Antimicrobial activity was evaluated against the bacterial strains e.g., Eschericha coli (MTCC 443), Pseudomonas aeruginosa (MTCC 1688), Staphylococcus aureus (MTCC 96), Streptococcus pyogenes (MTCC 442), H37Rv strain of Mycobacterium tuberculosis, and the antifungal activity was observed against strains e.g., Candida albicans (MTCC 227), Aspergillus niger (MTCC 282) and Aspergillus clavatus (MTCC 1323). All the synthesized compounds were found to possess moderate to excellent activity against selected strains.