4-Thiazolidinone derivatives of 2-((1H-benzo[d]imidazol-2-yl) thio) aceto hydrazide undergo condensation with benzaldehyde to give Arylidine derivatives (2a-e) in good yields. The cyclo condensation of compounds (2a-e) with Phenyl hydrazine yields Pyrazolo [3,4-d]thiazole derivatives (3a-e). The structures of all compounds were confirmed on the basis of analytical and spectral data. All the newly synthesized compounds were evaluated for their antibacterial and antifungal activities