Passenger ride comfort is an integral component of any road vehicle. Ride comport is impacted by vibration resulting from road roughness of low frequency, and also engine vibration of high frequency. The engine mount is an essential component, which acts as a vibration isolator from unwanted vibration. However, vibration isolation requires conflicting design criterion, such as high damping in low frequency range, and low damping in high frequency range. The purpose of this study was to develop a new optimal damping design method for engine mounts based on minimizing H_∞-norm. The damping minimizes H_∞-norm of displacement and force transmissibilities in the wide-frequency vehicle operating range. The proposed optimal damping control was applied to a Magnetorheological (MR) engine mount, to investigate the vibration isolation performance. The feasibility of the proposed method is verified, with some numerical simulation examples.