Equimolar amounts of melamine and levulinic acid results an organic crystal of melaminium levulinate monohydrate (MLM) at room temperature. MLM belongs to a monoclinic crystal structure having P2(1)/c space group which was confirmed by single crystal X-ray diffraction study. Functional groups present in the MLM crystal were identified by FT-IR spectral study. HRXRD study dictates the quality of MLM crystal. UV-visble spectrum of MLM reveals the lower cut-off wavelength of 293 nm with 55% optical transparency and optical band gap was found to be 4.20 eV for the prominent plane (1 0-1). Refractive indices for the three axes of MLM crystal were found to be n(x)=2.6, n(y)=2.4 and n(z)=2.2 respectively. Further the thermal stability and melting point of MLM crystal were investigated by TG/DTA study. Dielectric permittivity tensor components were estimated for the planes (1 0 - 1), (0 1 0) and (1 1 1) respectively. The thermal conductivity of the crystal by Wiedemann-Franz law was found to be 5.99 x 10(-11) W/mK at 70 degrees C. LDT value (2.84 GW/cm(2)) of MLM was estimated for laser optical device applications. (C) 2015 Elsevier B.V. All rights reserved.