The present study describes the synthesis, spectroscopic and electrochemical characterization of Cu(II)sulfathiazole (Hstz:4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide) complexes with dien (diethylenetriamine). The techniques used for the characterization have been single crystal X-ray diffraction, IR and EPR. The structural study indicated that the [Cu(stz)(2)dien] complex crystallizes in the monoclinic space group Pna2(1) with Z= 4. Two sulfathiazole anions were coordinated to the metal ion through N atom of the deprotonated sulfonamido group. Almost square-bipyramidal geometry with value of tau parameter approximate to 0.048 has been completed with three nitrogen atoms of dien molecule. The most important spectral features of the complex with its structural,properties were compared and discussed. The electrochemical study indicated the formation and the irreversibility of the mixed ligand metal complex. Biological study of the [Cu(stz)(2)dien]center dot 3H(2)O against Gram-positive and Gram-negative bacterial and fungal strains complex showed very strong antibacterial activity with MIC values ranging from 1 to 4 mu g/mL. (C) 2016 Elsevier Ltd. All rights reserved.