L-Histidinium bromide monohydrate (LHBr) single crystal is a nonlinear optical material. In this work the high temperature phase transformation and the thermal stability of single crystals of LHBr was investigated by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry and Raman spectroscopy. The results showed the LHBr phase transformation of orthorhombic (P2(1)2(1)2(1)) to monoclinic system (P 1 2 1) at 120 degrees C, with the lattice parameters a = 12.162(1) angstrom, b = 16.821(2) angstrom, c 19.477(2) angstrom and beta = 108.56(2)degrees. These techniques are complementary and confirm the structural phase transformation due to loss water of crystallization. (C) 2015 Elsevier B.V. All rights reserved.