The single crystals of pure glycine phosphite (pure-GPI) and potassium hydroxide doped glycine phosphite (KOH-GPI) were grown by slow evaporation and Sankaranarayanan and Ramasamy (SR) method. Colourless crystal with cylindrical shape about maximum diameter of 18 mm and 28 mm length was obtained with in a month. The morphologies were analyzed for the pure and KOH-GPI crystals which are grown by slow evaporation method. For both the crystals the crystal system was found to be monoclinic based on the single crystal X-ray diffraction analysis. The crystalline quality has been analyzed for both the compounds by the powder X-ray diffraction studies. From differential thermal analysis data of both the compounds were compared. From Vickers indentation method, Meyer’s index number (n) and hardness value of the crystal was calculated. Young’s modulus, anisotrophy nature of the crystal and Brittleness property were analyzed for both the samples.