The Schiff base compound (Z)-4-methyl-N-[2-((2-oxonaphthalen-1(2H)-ylidene)methylamino)ethyl]-benzenesulfonamide has been synthesized and characterized by IR, UV-Vis and single-crystal X-ray diffraction. Molecules of the title compound exist as NH tautomeric form in solid state. Molecular geometry and vibrational frequencies of the compound in the ground state have been calculated using the density functional theory (DFT) with 6-31G(d,p) basis set and compared with the experimental data. The calculated results show that the optimized geometry can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies are in good agreement with the experimental values. In calculation of electronic absorption spectra, TD-DFT calculations were carried out in the both gas and solution phases. The energetic behavior of the compound in solvent media has been examined using B3LYP method with the 6-31G(d,p) basis set by applying the polarizable continuum model (PCM). The total energy of the compound decreases with increasing polarity of the solvent. Besides, molecular electrostatic potential (MEP) and non-linear optical (NLO) properties of the title compound were investigated using theoretical calculations. (C) 2012 Elsevier B.V. All rights reserved.