In the title compound, [Co(C(2)H(8)NO(6)P(2))(2)(H(2)O)(2)]·9H(2)O, the Co(II) atom has a slightly distorted octa-hedral coordination environment consisting of four deprotonated phospho-nate O atoms of two independent 1-amino-ethyl-idendiphospho-nate anions and complemented by the O atoms of two water mol-ecules in cis positions. The anions exists in the zwitterionic form (protonated amino group and two deprotonated phospho-nate O atoms) and constitute two six-membered chelate rings. The crystal structure also contains nine partly disordered uncoordinated water mol-ecules, which create an extensive three-dimensional network of strong O-H⋯O and N-H⋯O hydrogen bonds.