Aromatic/heteroaromatic Schiff base was synthesized by the reaction of 2-amino-6-methyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile with 2,3-dihydroxybenzaldehyde. Titled compound was characterized by elemental analysis, FT-IR, 1H NMR, 13C-APT NMR and single crystal X-ray diffraction methods. Imine compound was crystallized in triclinic crystal system with space group P-1. X-ray studies reveal that our molecule is stabilized by O-H···N and C-H···O hydrogen bonds and intermolecular π∙∙∙π interactions. The molecular structure of Schiff base was optimized by density functional theory (DFT) method using B3LYP/6-311+G(2d,p) quantum set in Gaussian 09W software program. The chemical shifts and geometrical parameters were also computed by the same quantum level and compared with the experimental results of (E)-2-(2,3-dihydroxy)-benzylidene)amino)-6-methyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile.