New single crystals of L-citrulline oxalate (LCO) monohydrate are grown from aqueous solution by slow evaporation technique. Structure and morphology of the grown crystals are identified by single crystal XRD. The compound crystallizes in the orthorhombic structure with space group P2(1)2(1)2(1), having cell parameters, a = 5.208(5) angstrom, b = 9.829(5) angstrom and c = 23.879(5) angstrom. Powder X-ray diffraction data is used for the assignment of the hkl values. The chemical composition of the synthesized crystals is verified by CHN analysis. Functional groups present in the sample are identified by Fourier transform infra red (FT-IR) and FT-Raman spectral analysis. The second harmonic signal generated by the crystal using pulsed Nd: YAG Laser is confirmed by the emission of green radiation, showing that the crystal is a potential candidate for nonlinear optical studies. (C) 2011 Elsevier B.V. All rights reserved.