The new sulfonamide compound (C18H14Cl2N2O4S2) has been isolated from the reaction of 4,5-dichloro-1,2-diaminobenzen and benzensulfonyl chloride in the presence triethylamine in THF. X-ray diffraction, Hirshfeld surface analysis, FT-IR, NMR, and UV-vis spectroscopies were applied to characterize the composition and crystal structure of the compound. The molecular structure in the ground state was optimized using density functional theory (DFT/B3LYP) method with the 6-311++G(d,p) basis set and compared with the results of X-ray diffraction. The theoretical equivalents of all the experimental spectroscopic data together with the molecular electrostatic potential and frontier orbitals were also obtained at the same level and discussed. In general, an acceptable agreement is seen between the experimental and theoretical ones.