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, H-1-NMR, C-13/APT-NMR and X-ray diffraction methods. Imine compound was crystallized in triclinic crystal system with space group P-1. Xray studies reveal that our molecule is stabilized by O-H center dot center dot center dot N and C-H center dot center dot center dot O hydrogen bonds and intermolecular pi center dot center dot center dot pi 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.