Deep‐eutectic solvents (DESs) are regarded as alternative green solvents to ionic liquids. In this work we report the structural properties and hydrogen bonding (H‐bonding) interactions of an aqueous DES system. The used DES, ethaline (ETH), is composed of choline chloride and ethylene glycol (EG) in 1 : 2 molar ratio. The investigations were carried out by FTIR spectroscopy combined with quantum chemical calculations. Excess spectroscopy and two‐dimensional correlation spectroscopy (2D‐COS) were used to explore the data in detail. The results showed that, upon mixing, ETH transforms to EG dimers and trimers and D₂O clusters transform to various ETH‐D₂O complexes. Theoretical calculations show that water molecules insert between the anion and cation of ETH, break the strong doubly ionic Cl^−…H−O_Ch+ H‐bond, share charges of the ions and form H‐bond with them, thus modulate the interaction properties of ETH. This study deepens our molecular‐level understanding of the system and would shed light on its applications.