Arterial hypertension is a very common disease, which is treated with different medications such as Irbesartan. This compound is a nonpeptide antagonist of the receptor of the enzyme angiotensin II. The infrared and Raman spectra of this compound were recorded and discussed assisted with density functional theory using the 6-31G** basis set and animated pictures. Irbesartan exists in two tautomeric forms which can be isolated in the solid state. The vibrational study has been recorded using a mixture of both forms. ¹³C, ¹⁵N and ¹H NMR theoretical studies have been performed and compared with previously reported experimental data. Theoretical calculations allowed the determination of the main features of the A and B tautomers of Irbesartan both in the vibrational studies and in the NMR spectroscopy.Centro de Química Inorgánica