In the novel title binuclear zinc(II) Schiff base complex, bis(mu-11-thiosemicarbazonoindeno[1,2-b]quinoxaline-8-carboxylato)bis[(dimethyl sulfoxide)zinc(II)] dimethyl sulfoxide trisolvate, [Zn2(C17H9N5O2S)2(C2H6OS)2].3C2H6OS, each ZnII atom is five-coordinated and situated in a distorted square-pyramidal environment, coordinated by two L2- ligands and one dimethyl sulfoxide molecule. Each L2- ligand, which coordinates to two ZnII atoms, has two parts. One part, acting in a tridentate chelating mode, coordinates to one ZnII atom through two N atoms and one S atom, while another part coordinates to another ZnII atom through a monodentate carboxylate group. The whole complex has a dimeric structure. The coordination mode of the nearly planar L2- ligand is quite different from the most common mode for Schiff bases.