Four series of novel mixed ligand–drug complexes of thiamine hydrochloride as a primary ligand and four azo compounds, as secondary ligands, were prepared using Co (II), Ni (II), Cu (II) and Zr (IV) ions. The complexes were characterized by elemental analysis, thermogravimetric analysis, molar conductivity, FT-IR, magnetic susceptibility and UV-Visible spectroscopy. Based on the analytical and spectral data, the complexes were formulated as [Azo – M – Thiamine (H2O)n]+Cl- where n=2 for Co (II), Ni (II) and Cu (II) and=1 for Zr (IV). All the complexes possessed octahedral geometry in which both the primary and secondary ligands act as monovalent monodentate coordinated via ON fashion in case of azo compounds and via OS fashion in case of thiamine hydrochloride. Biological activity of some complexes has been evaluated against a number of pathogenic bacteria and fungi. Obtained results indicated that the metal complexes exhibited better antimicrobial and antifungal activities