Aqueous solutions of tetrahydrofuran (THF) represent a structurally complex binary system governed by the competition between hydrogen bonding in water and specific solute–solvent interactions. While the acoustic properties of THF–water mixtures have been extensively studied in the ultrasonic frequency range, their behavior at hypersound (gigahertz) frequencies remains insufficiently explored. In this work, the concentration dependence of hypersound velocity and relaxation times in the THF–water system is investigated using Brillouin light scattering at scattering angles of 90° and 180°.