Single crystals of L-Histidinium semisuccinate were grown by slow cooling technique. Single crystal X-ray diffraction study confirms the formation of the crystal structure. Vickers microhardness studies were carried out on the grown crystals of L-Histidinium semisuccinate over a load range of 10-500 g. It was found that the grown crystal exhibits normal indentation size effect as the hardness number decreases with increase in load. The Meyer’s index number ‘n’ was found to be greater than 1.6, showing the grown crystal belongs to a soft material category. The resistance pressure ‘W’ was calculated using Hays-Kendall approach. The values of fracture toughness (Kc) were determined from the measurements of crack lengths and the types of cracks were identified. Brittleness indexes (Bi) and yield strength (σy) were also assessed from the values of Vickers hardness number (Hv). The elastic stiffness coefficient (C11) values have been calculated using Wooster’s empirical formula. The results were discussed in detail. © RASĀYAN. All rights reserved.