Organic non-linear optical single crystal 4-methoxy benzaldehyde - N -methyl - 4 - stilbazolium tosylate (MBST) has been synthesised and grown by slow evaporation technique. The grown crystals were analyzed by various instrumentation techniques. The crystal system and lattice parameters were found from single crystal X-ray diffraction. The crystalline perfection is quite good as observed from the high resolution X-ray diffractometry. The FTIR spectrum gives the detail about the various functional groups present and the UV−vis−NIR studies show that the crystal is optically transparent in the wavelength range of 440−1100 nm. The powder SHG studies were done with Kurtz powder technique and the NLO efficiency is 17.2 times greater than urea. Mechanical behavior was analyzed using Vicker’s microhardness test. Microhardness studies revealed that the hardness of the grown crystal increases with an increase in load. Meyer’s index number n was calculated and found that the material belongs to soft material category.