This article proposes a disturbance observer-based event-triggered H∞ controller for a semi-active seat suspension that equips an advanced electromagnetic damper (EMD) system. Automated driving is one of the leading technologies of the automotive industry. However, automated vehicles (AVs) may increase the incidence of motion sickness (MS) and deteriorate motion comfort. This article investigates a semi-active seat suspension system and an advanced controller to improve the motion comfort of AVs. The disturbance force of the seat suspension has considerable influence on the system dynamic, and applying a constant model to describe the real-time disturbance force is unreliable. Therefore, a disturbance observer is designed to estimate the seat suspension disturbance force, and it is used to compensate the controller. The Bouc-Wen model is selected to compare with the disturbance observer and validate its effectiveness. Then an event-triggered H∞ controller combined with the disturbance observer is proposed. The performance of the proposed controller is validated with experiments. Experimental results show that the proposed event-triggered H∞ controller not only can save the communication resources of data transmission but also can work as a filter to increase motion comfort.