In this work, organic new bis (2-amino-6-methylpyridinium 3,4-dimethoxybenzoate) dihydrate (2A6MD) single crystal was grown by slow evaporation method with the dimensions 20 × 4 × 10 mm3. The structure of grown crystal was confirmed via the single crystal X-ray diffraction. It showed that 2A6MD compound crystallizes in a monoclinic crystal system with Centro symmetric space group P21/n. Powder X-ray diffraction analysis confirmed the crystalline nature 2A6MD crystal. FT-IR and 1H NMR spectra were carried out to confirm the functional groups and various hydrogen exposures in the 2A6MD crystal. UV-Vis spectrometer studies showed that 2A6MD crystal has a lower cut-off wavelength in the UV region and good optical transmittance in the entire visible region. Photoluminescence spectrum reveals the high emission peak at 366 nm with an excitation wavelength of 334 nm. Thermal stability and melting point of the synthesized 2A6MD crystal were investigated using TG-DSC measurement. Vickers's micro hardness test declares that mechanical stability of the grown crystal and their yield strength, elastic stiffness values were evaluated. The chemical etching was analyzed on the 2A6MD surface and the results expressed the growth feature of the crystal. Nonlinear absorption co-efficient, nonlinear refraction and third order susceptibility of synthesized 2A6MD crystal was evaluated by the Z- scan method. The density functional theory (DFT) computations with B3LYP/6-311++G (d,P) basis set to theoretically optimize the molecular geometry, HOMO-LUMO energies, molecular electrostatic potential, NBO analysis and first order hyperpolarizability of 2A6MD confirmed the nonlinear property. © 2021 The Physical Society of the Republic of China (Taiwan)