Reaction of pyridoin with nickel nitrate in methanol in air gives crystals of two forms of the title compound, [Ni(C(12)H(9)N(2)O(3))(2)]; a triclinic form with the Ni atom on an inversion centre and a monoclinic form with one molecule in a general position in the asymmetric unit. Both forms show an octahedral nickel centre coordinated by two facial tridentate ligands with their O-atom donors trans.