A single crystal of nonlinear optical material Benzimidazolium Benzilate (BDBA) with dimensions 0.2 × 0.2 × 0.18 mm3 was successfully grown by slow evaporation technique. The BDBA crystal crystallizes in the monoclinic crystal system with centrosymmetric space group C2/c. The intermolecular interactions were estimated through the Hirshfeld surface analysis. The vibrational modes of functional groups present in the compound were confirmed through attenuated total reflectance spectral studies. The molecular structure of BDBA was ascertained using NMR spectroscopic measurements, and the results confirmed the migration of proton from benzilic acid to Benzimidazole. Photoluminescence spectra indicate violet fluorescence emission peaks at 350 nm excitation. The optical band gap was 4.39 eV with a transmittance cut off wavelength of 282 nm. The extinction coefficient, optical and electrical conductivity, susceptibility, and polarization were calculated using UV–Vis-NIR spectroscopic measurements. The thermal properties were assessed by the simultaneous study of thermogravimetric (TG) and differential thermal analysis (DTA). It shows that the compound withstands up to a temperature of 148 °C. The crystal properties were theoretically computed using density functional theory (DFT) at the level of RB3LYP/6–311 + G(d,p) and computational studies such as natural bond orbital analysis, molecular electrostatic potential, Mulliken atomic charge distribution, and HOMO-LUMO were performed. The third order nonlinear optical (NLO) properties were studied using Z-scan studies. © 2021