N-Methylurea oxalic (NMUO) acid organic crystals were grown by solution method with slow evaporation solution technique (SEST) in aqueous solution. Using single crystal XRD (SCXRD) analysis, the structure of the crystal was determined. The powder X-ray diffraction (PXRD) study reveals that the crystallinity of the specimen. The functional groups of the title molecule were determined from FTIR and FT-Raman analyses. Optical transmittance of the crystal was studied using UV–Visible spectroscopy. The hardness of the grown crystal was found by Vickers microhardness test. The dielectric behavior of the crystal was determined at 30 ºC temperature. The thermal stability of the crystal was studied by thermogravimetric analysis (TG/GTG) and differential scanning calorimetry (DSC). Z-scan characterization was carried out to investigate the third-order nonlinear optical properties of the crystal. © RASĀYAN. All rights reserved.