The title compound {sys-tematic name: bis(μ(2)-dihydrogen 4-aza-niumyl-1-hy-droxy-butane-1,1-di-phos-pho-n-ato)bis-[aqua-(dihydrogen 4-aza-nium-yl-1-hy-droxy-butane-1,1-diphospho-n-ato)nickel(II)] dihydrate}, [Ni(2)(C(4)H(12)NO(7)P(2))(4)(H(2)O)(2)]·2H(2)O, was synthesiized under hydro-thermal conditions. Its structure is isotypic with the Co(II) analogue. The crystal structure is built up from centrosymmetric dinuclear complex mol-ecules and the structure is reinforced by a net of inter-molecular O-H⋯O and N-H⋯O hydrogen bonds. One water mol-ecule is bound to the Ni(II) atom in the octahedral coordination sphere, while the second is part of the inter-molecular hydrogen-bond system.