The structure of the title compound, [Ni(NO(3))(C(18)H(12)N(2))(H(2)O)(2)]NO(3) x H(2)O, is composed of monomers with the nickel ion octahedrally coordinated to a bidentate biquinoline ligand, a bidentate nitrate anion and two water molecules, and is stabilized by a nitrate counter-ion and a hydrate water molecule. There is a fairly complex hydrogen-bonding scheme involving all the water H atoms and five different nitrate O atoms.