The title compound has been synthesized by grinding in an agate mortar. Its structure was characterized by TGA-DSC studies, FT-IR, X-ray powder diffraction data, and single-crystal X-ray diffraction. This compound crystallize in the monoclinic system with space group P2(1)/c, Z = 4, and unit cell parameters a = 6.9834(4) angstrom, b = 9.8771(6) angstrom, c = 13.6740(8) angstrom, and beta = 103.861(1)degrees. The salt, C6H7N2O+center dot C2H2NO3-, or NA(+):OXAM(-), is an ionic ensemble assisted by hydrogen bonds established between nicotinamidium cations and oxamate anions. The molecular structure and crystal packing are stabilized mainly by four intermolecular N-H center dot center dot center dot O hydrogen bonds, reinforced by two C-H center dot center dot center dot O hydrogen bonds and three intramolecular interactions. The two components thus construct a supramolecular assembly with a three-dimensional hydrogen bonded framework.