The synthesis and crystal structure of the mononuclear title compound, [Co(C(2)O(4))(C(10)H(8)N(2))(2)].5H(2)O, is reported. The Co atom is six-coordinated by two O atoms of a bidentate oxalate group and by four N atoms of two bipyridine ligands. The neutral [Co(C(2)O(4))(C(10)H(8)N(2))(2)] entities are connected by pi-pi stacking interactions of the aromatic systems into a two-dimensional layer, interconnected through a ladder-like hydrogen-bonding pattern of solvate water molecules.