In the title compound, [Co(C(16)H(19)N(2)O(2))(2)]NO(3)·H(2)O, the Co(III) ion is located on an inversion center and is six-coordinated by two phenolate O atoms and four amino N atoms from two diamine ligands, forming an octa-hedral geometry. The water mol-ecule and the nitrate anion are located close to an inversion center, and are thus equally disordered by symmetry. The crystal packing is stabilized by inter-molecular O-H⋯O hydrogen bonds involving the uncoordinated water mol-ecule and the free phenol hydroxyl group with the nitrate anion. N-H⋯O hydrogen bonds involving the amino groups and the nitrate anions connect the complex mol-ecules along the c axis.