The complex cation of the title compound, [Co(C12H8N2)3]2(NO3)4·C12H12N2O6·8H2O, contains a Co(II) atom with a distorted octa-hedral coordination environment defined by six N atoms from three bidentate 1,10-phenanthroline ligands. The asymmetric unit of the title compound is completed by one-half of the N,N'-(1,4-phenyl-enedicarbon-yl)diglycine solvent mol-ecule, which is located on a centre of inversion, by two nitrate counter-anions and four solvent water mol-ecules. Two [Co(C12H8N2)3](2+) cations are connected through C-H⋯O contacts and through lone-pair⋯π inter-actions involving the non-coordinating N,N'-(1,4-phenyl-enedicarbon-yl)diglycine and phenanthroline mol-ecules. The different aromatic ring systems are involved in π-π stacking and C-H⋯π inter-actions, with centroid-to-centroid distances in the range 3.7094 (8)-3.9973 (9) Å. The crystal structure is stabilized by further anion⋯π inter-actions and C-H⋯O contacts, as well as O-H⋯O and N-H⋯O hydrogen bonds between water mol-ecules, the non-coordinating nitrate anions, N,N'-(1,4-phenyl-enedicarbon-yl)diglycine and phenanthroline mol-ecules. These non-covalent inter-actions give rise to a three-dimensional supra-molecular network.