<p>A novel organic nonlinear optical (NLO) crystal of creatininium 4-aminobenzenesulfonate (CABS) is obtained through the slow evaporation technique and the molecular structure is detected by the single crystal X-ray diffraction method. The density functional theory (DFT) method with B3LYP/6-311G (d, p) basis set is used to optimize the structure and to determine the structural parameters. The FT-IR and FT-Raman spectral analysis is carried out to identify the functional groups present in the molecule. The molecular elucidation of CABS is done with the aid of ¹³C and ¹H NMR spectroscopic studies. The stability of the molecule, intermolecular hydrogen bonding and hyperconjugative interaction of CABS are determined by making use of natural bond orbital (NBO) analysis. Molecular electrostatic potential (MEP) is utilized for discerning the reactive sites for electrophilic and nucleophilic attacks. Topological analyses are performed to investigate the intra and intermolecular interactions especially the characteristics of N–H...O hydrogen bonds. To discern the contribution of intermolecular interactions, Hirshfield surface analysis and fingerprint plot are carried out. The UV–visible analysis reveals that the synthesized CABS crystal exhibits good optical activity and the minimum Urbach energy indicates that the crystal possesses well-defined crystalline quality. The nonlinear optical (NLO) parameters are theoretically evaluated by the same DFT theory. The capability of the crystal to withstand laser power is investigated using laser damage threshold (LDT) studies. The third-order nonlinear optical parameters of the CABS compound are determined by the Z-scan technique and are found to be higher than other related compounds. The obtained result shows that the CABS crystal is a good candidate for nonlinear optical applications.</p>