A new complex of Cu(II), the composition Cu(C3H7N3O4S)∙H2O, the reaction of thiosemicarbazone glyoxylic acid with copper nitrate in an aqueous medium was synthesised. X-ray diffraction analysis established the composition of the complexes was studied by IR, UV electronic absorption and EPR spectroscopy, and thermogravimetry. Thermogravimetry shows five stages of decomposition in the temperature range 90-990°C. The magnetic susceptibility of the complex is studied. The value of μeff for the complex is 1.76 BM, which is close to the value of one unpaired electron (1.73 BM). The ligand coordinates with the metal atom and consists of monoanionic Cu(C3H7N3O4S)∙H2O polymeric complex connected by Cusbnd N bonds with neighbouring molecules. The metal centre coordinates with the oxygen of carboxylic, sulfur of thiolic and nitrogen of the azomethine group. The X-ray data and ESR spectra specify a distorted square pyramidal environment around Cu(II) ion.