In the polymeric title copper(II) compound, [Cu(CHO(2))(2)(C(8)H(6)N(2))](n), both formato ligands are O-bidentate anions and act as bridging ligands, creating a planar polymeric arrangement. The slightly distorted square-pyramidal coordination around Cu(II) comprises four O atoms from two different formate anions as the base and a quinoxaline mol-ecule in the apical position.