One potentially bioactive ligand, 2,5-diamino-1,3,4-thiadiazole(L), derived from cyclisation of bithiourea in a 3% hydrogen peroxide medium were prepared and characterized. The complex of the type ML2, (M= Zn) were prepared. The complex is non-electrolyte in DMF. The elemental analysis, magnetic measurements, conductivity measurements and spectral studies of the complex were carried out. 2,5-diamino-1,3,4-thiadiazole acts as neutral tridentate ligand and coordinates through the sulphur atom and nitrogen of the amines. It was tentatively inferred that complex exhibited octahedral geometry. The antimicrobial activities of ligand and its complex were screened using sensitivity test, minimum inhibition concentration and minimum bacterial concentration method. Metal chelate showed greater antimicrobial activities as compared to the control and the ligand. The metal chelate and the ligand did not exhibited activity against Aspergillus niger and Penicillin species. The toxicological study carried out on albino rat (Wistar strain) showed that the ligand and the metal chelate do not show toxicity at the orally administered dosage-level (0.6 mg/kg body weight).