The Mannitol single crystal was grown by slow evaporation technique and irradiated by gamma radiation. Single crystal XRD analysis showed that irradiation not changed the crystal system. The crystalline perfection of pure and irradiated Mannitol single crystal were studied by high resolution X-ray diffraction analysis. The optical behaviour of pure and irradidated Mannitol was verified by the changes in the affected cut-off wavelength. The laser damage threshold was calculated for pure and irradiated Mannitol using laser source. The second harmonic generation of pure and gamma irradiated Mannitol were studied using Nd:YAG laser source and observed that SHG intensity decreases with increasing dose of gamma radiation.