The growth and properties of new semiorganic nonlinear optical crystal, tetra L-lysine alanine mono hydrochloride dihydrate (TLAMHC1) have been studied. TLAMHC1 crystals were grown from aqueous solution by slow cooling technique. Solubility of the synthesized material has been determined for various temperatures using water as solvent. Spectral, thermal and optical techniques have been employed to characterize the new materials. Bulk single crystals of size 2.3 cm x 1.7 cm x 1.3 cm of TLAMHC1 have been grown by slow cooling method. The powder X-ray diffraction pattern of the grown TLAMHC1 has been indexed. Functional groups present in the sample were identified by FTIR spectral analysis. Thermal stability of TLAMHC1 was determined using TGA/DTA curves. Vicker's microhardness study was carried out at room temperature. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for optical second harmonic generation. The second harmonic generation (SHG) efficiency of TLAMHC1 was found to be 1.2 times that of potassium dihydrogen phosphate (KDP). (c) 2007 Published by Elsevier B.V.