<p>Bis(4-methylbenzylammonium) adipate adipic acid (4MLBAA), a new organic crystal has been developed using solvent evaporation method. The structure of 4MLBAA has been solved and it reveals the monoclinic crystal system and P2₁/n space group. Cell parameters, bond distance, bond angle and torsion angles are also determined using Single crystal X-ray diffraction analysis (SCXRD). In this structure, bis(4-methylbenzylammonium) (C₈H₁₂N⁺⁾ cation, one half of (C₆H₈O₄²⁻) anion and one half of neutral (C₆H₁₀O₄) molecule are connected through N–H⋯O, C–H⋯O and O–H⋯O hydrogen bonds. Powder X-ray diffraction (PXRD) analysis shows that the sharp peaks are due to the excellent crystalline nature of 4MLBAA crystal. The transmission window has been noticed from 261 to 1100&#xa0;nm and the linear parameters such as energy gap (Eg), extinction coefficient (k), reflectance (R) and refractive index (n) are identified using UV–Vis–NIR spectrum analysis. Functional group vibrational modes are analyzed by FT-IR and FT-Raman spectroscopy. ¹H and ¹³C NMR study reveals the molecular structure of 4MLBAA crystal. Photoluminescence measurement reveals that 4MLBAA crystal has two high intensity emission at 247 and 260&#xa0;nm and a low intensity emission at 320&#xa0;nm signifies the near ultraviolet emission of the crystal. The nonlinear optical parameters have been analyzed by Z-scan method. The third order nonlinear optical susceptibility (χ³) value of 4MLBAA crystal is estimated as 1.289 × 10^–6 esu. Self-defocusing and saturable absorption nature of 4MLBAA crystal has been obtained from closed and open aperture traces. The observed results find its application in sensor devices and optical switching.</p> Graphical abstract <p></p>