Reactions between CuX2 (X=Cl, Br) and 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline (DPhPyTn) yield the complexes [{CuCl(DPhPyTn)}2(μ-Cl)2] (1), [CuBr(DPhPyTn)2]Br (2) and [{CuBr(DPhPyTn)}2(μ-Br)2] (3). Copper(II) complexes have been characterized by elemental analysis, IR, electronic spectra, single crystal X-ray diffraction and magnetic susceptibility measurements. Likewise, the crystal structure of DPhPyTn has been determined. Complexes 1 and 3 are dimeric molecules in which copper ions are bridged by two halide anions whereas 2 is a monomeric unit. The geometry around the copper(II) center in the dimeric units is a distorted squared pyramid, while in the monomeric compound is a distorted trigonal bipyramid. The magnetic susceptibility data of dimeric compounds were followed by the Bleaney–Bowers dimer equation with J=−1.17 and −2.36cm−1 for the chloro and bromo complexes respectively, indicating that there are weak antiferromagnetic interactions between the copper(II) ions in the solid state.