In the title compound, [Co(NO(3))(2)(C(20)H(18)N(4))](n), the Co(II) atom lies on a crystallographic twofold axis and the coordination geometry can be considered as a slightly distorted tetra-hedron defined by two O atoms from two nitrate groups and two N atoms from two ligand mol-ecules. A distorted octa-hedron may be assumed when two of the symmetry-related nitrate O atoms with Co-O distances of 2.3449 (19) Å are added to the coordination environment. Another twofold axis, passing through the middle of the biphenyl bonds, is observed in the crystal structure. A chain is built up by the ligands linking the Co(II) ions along [101].