1-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylmethanamine (1) react with chloro acetic acid and hydrazine hydrate gives 2-(2-((dimethylamino)methyl)-1H- benzo[d]imidazol-1-yl)acetohydrazide (2),Which on reaction with CS2/KOH gives 5-((2-((dimethylamino)methyl)-1H-benzo[d]imidazol-1-yl)methyl)-1,3,4-oxadiazole-2(3H)-thione (3). The compound (3) on Mannich reaction gives different 3-((dialkylamino)methyl)-5-((2-((dimethylamino) methyl)-1H-benzo[d]imidazol-1-yl)methyl)-1,3,4-oxadiazole-2(3H)-thione (4a-e). The structures of these compounds were established on basis of analytical and spectral data. The newly synthesized compounds were evaluated for their antibacterial and antifungal activities.