The crystal and molecular structure of the bis(μ-benzoato-O, O′) (dimethylsulphoxide) copper (II), [Cu(C 6H 5COO) 2(DMSO)] 2 (where DMSO is dimethylsulphoxide) were determined by the heavy-atom technique. The compound crystallizes in the monoclinic space group C2/c with four dimeric formula units in a cell with dimensions a = 19.030(8) Å, b = 15.494(9) Å, c = 23.828(11) Å, and β = 103.73(4)°. The observed and calculated densities are both 1.49 g cm −3. The structure was refined by full-matrix least-squares methods to a final value of the R factor of 0.071, based on 1892 independent data with 1 ⩾ 1.96 σ(I). The compound is dimeric, with square pyramidal geometry at each copper center. Two copper atoms bridged by four carboxylate groups while the apical ligand is DMSO. The ▪ distance is 2.627(3) Å. The Cu atoms are displaced by 0.197 Å (Cu 1) and 0.207 Å (Cu 2) from the plane containing four oxygen atoms towards the ligands DMSO. The magnetic susceptibility of the compound was measured as a function of temperature, and the data fitted to a Bleanay-Bowers equation which yields a singlet-triplet separation of 304 cm −1. The EPR spectrum of the powdered solid is consistent with a spin of S = 1. The data are compared with those found in similar copper(II) benzoates.