Seven new copper(II) complexes with 1-phenyl-3-methyl-4-azopyrazol-5-one were synthesized and isolated in the crystalline state. The crystal and molecular structure of the complex Cu(C 17H 15N 4O) 2·0.222H 2O was studied by X-ray diffraction. The organic ligand is coordinated to copper in the anionic form in the bidentate chelating mode through the oxygen atom of the pyrazolone moiety and one nitrogen atom of the azo group. As a first approximation, the copper(II) coordination polyhedron (CP) is a tetrahedrally distorted square. The copper CP is completed to an extended tetragonal pyramid (4+1) by the Cu·N(1) contact (3.072 Å) with the pyrazole nitrogen of the neighboring molecule. © Pleiades Publishing, Ltd., 2012.