In the title compound, [Co(C(8)H(8)O(4))(C(12)H(8)N(2))(H(2)O)(3)], the Co(II) atom is coordinated by two N atoms from a bidentate 1,10-phenanthroline ligand, one O atom from a monodentate 4-cyclo-hexene-1,2-dicarboxyl-ate ligand and three water O atoms in a distorted octa-hedral geometry. The mononuclear mol-ecules are engaged in extensive intra- and inter-molecular O-H⋯O hydrogen-bonding inter-actions and π-π stacking inter-actions [centroid-centroid distance = 3.784 (3) Å], forming a three-dimensional supra-molecular network.