A potentially useful semi-organic nonlinear optical single crystal of L-histidinium dinitrate (LHDN) has been synthesized and grown at room temperature by slow solvent evaporation method. The resulting crystals predominantly exhibit the needle morphology. The title compound has been subjected to single-crystal X-ray diffraction analysis to identify the unit cell parameters and morphology. The crystalline perfection of LHDN has been evaluated by high-resolution X-ray diffractometry (HRXRD). The transparency of the crystal was checked by UV-vis-NIR study. Thermal stability of LHDN investigated by TG/DTA and DSC analyses confirms that the compound is stable up to 165.5 degrees C. The second-harmonic generation efficiency was estimated by Kurtz and Perry powder technique and the study clearly suggests the influence of particle size on the SHG efficiency of LADN. (C) 2007 Elsevier B.V. All rights reserved.