The solvent effect on the molecular structures of copper(II) complexes produced from the reaction between CuBr(2) and 1,10-phenanthroline is evident. The monomeric title compound, [CuBr(2)(C(12)H(8)N(2))(C(2)H(6)OS)], which consists of discrete units, is produced from this reaction in dimethyl sulfoxide (DMSO), whereas a polymeric copper(II) compound is known to be produced from the same reaction in the poor coordinating solvent ethanol. The geometry around the copper(II) ion in the title compound is best described as trigonal-bipyramidal distorted square-based pyramidal, with a tau value of 0.37. The two phenanthroline N atoms, the DMSO O atom and one of the Br atoms occupy the four basal positions, while the second Br atom occupies the axial position. The magnetic susceptibility data also indicate that the title compound is monomeric, but there is still a weak antiferromagnetic interaction between paramagnetic copper(II) centers via the intermolecular 'Cu-Br...Br-Cu' contact pathway.