<p>Organic 2-amino-4,6-dimethylpyrimidium 3,5-dinitrobenzoate dihydrate (2APDBD) was synthesized and crystal were grown by the slow evaporation solution technique (SEST). Hirshfeld surface analysis was performed to investigate the electron density boundaries between molecules within the crystal lattice, providing insights into the nature of intermolecular interactions. The crystal structure of 2APDBD was confirmed by single-crystal X-ray diffraction (SXRD) and it was found to be triclinic system with the centrosymmetric space group P-1. Powder X-ray diffraction (PXRD) analysis of the ground sample confirmed the phase purity by comparing the experimental pattern with standard CIF data, and the peaks were indexed using corresponding Miller indices. The various functional groups of the grown crystal were identified using Fourier transform infrared (FTIR) spectroscopy. The transmittance of the grown crystal was analyzed by using UV–visible–NIR spectrum analysis and the cut-off wavelength was found to be 350 nm. Chemical etching study was carried out and the etch pit density (EPD) was calculated. The photoconductivity study reveals that the grown crystal has a positive photoconductive nature. The third-order nonlinear optical properties like refractive index (<i>n</i>₂), absorption coefficient (<i>β</i>), and susceptibility (<i>χ</i>⁽³⁾) were studied using Z-scan technique at 632.8 nm of He–Ne laser.</p>