Molecular dynamics simulations have been carried out to investigate the properties of a monolayer of diethylene glycol monododecyl ether (C₁₂E₂) adsorbed at the air/water interface at a surface coverage corresponding to that at its critical micelle concentration (34 Ų/molecule). The estimated thickness of the adsorbed layer was in good agreement with neutron reflection data. It was observed that the water molecules have a strong tendency to form hydrogen-bonded bridged structures with the oxygen atoms of the same surfactant chain. This resulted in an exclusive preference for the C−C bonds in the headgroup to attain gauche conformation. It was observed that the long polar headgroups were more tilted toward the aqueous layer because of strong interactions between them and water.