Tryptammonium hydrogentartarate (1) crystallizes in the orthorhombic space group P212121 and exhibits a crystal structure consisting of the tryptammonium cation, hydrogentartarate anion and a solvent methanol. The cations and anions are joined into a 3D network by intermolecular NH···OH(CH3) and NH3···O(tart) bonds with lengths of 2.998, 2.772, 2.902, and 2.847 Å, respectively. Hydrogentartarate anions are themselves connected by strong intermolecular O···H-O hydrogen bonds with lengths of 2.481 Å into infinite chains. The anions also participate in moderate hydrogen bonding with solvent methanol molecules of the (tart)O···O(CH3) type with bond lengths of 2.736 and 2.762 Å). The conformational preference of the tryptammonium cation is discussed by comparing the results with the data for other crystallographically determined structures of salts. Quantum chemical calculations at (density functional theory) DFT (B3LYP) level of theory and 6-311++G** basis set are performed for the interacting system tryptammonium cation/H2O with a view to predicting the geometry of the most stable conformer. The optical properties of tryptammonium hydrogentartarate have been elucidated in the solid-state by means of linear-polarized solid state IR-spectroscopy (IR-LD) of oriented solids as a colloid suspension in nematic hosts. Some limitations of the method are discussed as well.