In the title compound, [Ni(C(18)H(18)N(2)O(4))]·C(3)H(7)NO, the central Ni(II) atom is in a square-planar O(2)N(2) coordination environment. The planar Ni-salen moieties (r.m.s. deviation for the plane through the conjugated part of the Ni-salen group = 0.07 Å) form parallel stacks in the a-axis direction, with alternating Ni⋯Ni separations of 3.5339 (7) and 3.6165 (7) Å. In the crystal, there are weak inter-molecular C-H⋯O inter-actions involving the dimethyl-formamide O and phenolate O atoms.