Cobalt(II) nitrate hexa-hydrate and sodium dicyanamide self-assembled in dimethyl-formamide (DMF) and 4-methyl-pyridine solutions to form the title compound, [Co(C(2)N(3))(2)(C(6)H(7)N)(2)](n). The Co(2+) ion lies on an inversion center and adopts an octa-hedral coordination geometry in which four N atoms from four different dicyanamide ligands lie in the equatorial plane and two 4-methyl-pyridine N atoms occupy the axial positions. The Co(II) atoms are connected by two bridging dicyanamide ligands, resulting in a chain parallel to the c axis. The chains are connected into a three-dimensional network by C-H⋯N hydrogen bonds.