Single crystals of nonlinear optical material L-leucine were grown by slow evaporation at constant temperature 35 degrees C from its aqueous solution. Studies on structural, optical and dielectric properties of the crystal have been carried out by X-ray diffraction (XRD), infrared spectroscopy (IR). UV-vis-NIR transmission study, second harmonic generation (SHG) test and dielectric measurements. SHG efficiency of L-leucine is twice that of urea. L-leucine is thermally stable up to 268 degrees C. Morphology of the crystal is also determined by using crystallographic data. (C) 2012 Elsevier B.V. All rights reserved.