In the title compound, [Ni(C(2)O(4))(C(12)H(12)N(2)O)(2)](n), the Ni(II) atom, lying on a twofold rotation axis, is coordinated by two N atoms from two monodentate 3-(1H-imidazol-1-yl)-1-phenyl-propan-1-one (L) ligands and four O atoms from two oxalate anions in a distorted octa-hedral geometry. The oxalate anion has a twofold rotation axis through the mid-point of the C-C bond and acts as a bridging ligand, linking the Ni(II) atoms into a polymeric chain along [010]. Weak inter-molecular C-H⋯O hydrogen bonds connect the chains, resulting in a three-dimensional supra-molecular structure. >