Mono- and dinuclear Cu(I) and Cu(II) complexes of 1,3,4-mercapto-oxadiazole derivatives were prepared and characterized by elemental analyses and standard spectroscopic techniques. The complexes were formulated as Cu(G-OX)2, Cu2(G-OX)4(H2O)4, Cu(G-OX)2L2and Cu2(G-OX)2(PPh3)2; (G = H, MeO, Cl; L = Ph3P, Ph3As). The microbiological activity of the complexes was investigated against bacteria and fungi. All the complexes were active against Candida albicans, while the reactivity against bacteria varied. The antimicrobial activity of the [Cu(MeO-OX)2(H2O)2]2 complex was exceptionally better than that observed for any other metal complex against both bacteria and fungi.