The self-assembly of the title dinuclear complex, namely (mu-p-phenylenediamine-N,N,N',N'-tetraacetato)bis[aqua(1,10-phenanthroline)nickel(II)] dodecahydrate, [Ni(2)(C(14)H(12)N(2)O(8))(C(12)H(8)N(2))(2)(H(2)O)(2)].12H(2)O, through intricate noncovalent interactions results in a two-dimensional sheet-like structure. The dimer lies about an inversion centre at the centre of the p-phenylenediamine ring. Uncoordinated water molecules form one-dimensional chains in which cyclic water tetramers act as two types of building blocks. The water molecules play a significant role in the stabilization of the three-dimensional supramolecular framework. Intramolecular ;aryl-metal chelate ring' pi-pi interactions are also observed.