Organic bulk single crystal of cyclohexylaminium hydrogen phthalate hemihydrate (CYHPH) was grown by slow cooling method using methanol as a solvent. The grown crystal belongs to orthorhombic system with Pbcn space group and it has various functional groups such as NH3 +, phthalate and a water molecule. The cut off wavelength of CYHPH was found at 307 nm. Thermal analysis affirmed that the CYHPH compound was stable up to 146 °C and completely decomposed at 263 °C. The activation energy at 100 Hz, 1 and 10 KHz was found to be 0.31, 0.141 and 0.142 eV respectively. The grown CYHPH crystal exhibits third order nonlinear optical behavior. © 2017, Springer Science+Business Media New York.