Hydraulic mounts have been used underneath the powertrain of a vehicle to achieve better ride comfort. In this study, a transfer function model for a hydraulic mount, which is derived based on hydraulic dynamics, is adapted. Furthermore, an additional mode in high frequency range produced by the highly frequency dependent characteristics of a hydraulic mount is predicted theoretically, then, the existence of the extra vibration mode of the hydraulic mount is validated experimentally with a single mass and a single hydraulic mount system.