Thiabendazole-based metal complexes are attracting interest due to their special antimicrobial activities. The current investigation describes the preparation of ligand L1 and its metal complexes [M (C26H17N5OS) Cl2] M = Co, Ni, Cu and Zn. Mass, 1 H-NMR, IR, and UV were used to characterize these compounds. L1 exhibited the highest potency towards many bacteria. It shows the maximum zone of inhibition as compared to any other ligand. Thus, the antibacterial potency of L1 is better as compared to standard drugs. Imidazolone-TBZ ligands L1 are also more susceptible to some bacteria and also show antifungal potency against Pseudomonas aeruginosa. The significance of such work triggered the possibility that these ligands L1 and metal complexes can be efficacious drugs against bacterial and fungal species that could be advantageous in designing powerful antibacterial and antifungal compounds for medicinal use. All these synthesized compounds are in addition to the library of heterocyclic compounds.