The formazan derivatives (FM1–FM5) were synthesized by the reaction of benzaldehyde phenylhydrazone with substituted aromatic and hetero aromatic amines. The structures of the synthesized compounds were then elucidated using UV, IR, 1H NMR and mass spectral data. The synthesized derivatives were screened for anticonvulsant, antibacterial and antiviral activities. All the compounds showed remarkable antibacterial activity at 250 μg/ml, but FM4 and FM3 did not show any inhibition on Staphylococcus aureus and Vibriocholera, respectively. All the compounds showed significant anticonvulsant effect at 100 mg/kg p.o. and the experimental data were statistically significant at P<0.001 level. But none of the compounds was effective against Japanese encephalitis virus.