A series of novel acyl hydrazone derivatives of benzimidazole-2-thiol were synthesized. The acylhydrazide was condensed with a series of aromatic substituted aldehydes to yield the tetra decylhydrazone Schiff”s bases of benzimidazole-2-thiol. The acylhydrazide was taken in methanol in round bottom flask added 2-3 drops acetic acid and refluxed on hotplate the reaction mixture was monitored with TLC. After completion of reaction the product was precipitated in ice cool water, washed and dried. The synthesized compounds were screened for different biological activities such as antimicrobial, antihistamine, neutropic, analgesic, antiprotozoal, antimalarial, antiallergic, antioxidant, anticonvulsant, anti-tubercular and have shown a good results.