This paper proposes a hybrid controller for a seat suspension equipped with an advanced electromagnetic damper (EMD) system to meet the requirement with vibration isolation and energy saving. The friction of seat suspension has considerable influence on the system dynamic. Applying a constant model to describe the friction is unreliable due to the long term wear and tear. Therefore, an observer is designed to estimate seat suspension friction, and it is used to compensate for the frictional influence in a H∞ controller. The friction observer applies the acceleration, relative displacement and circuit current, which are measurable in engineering. Then, a hybrid controller is further proposed, in which the low-frequency vibration is controlled with the friction observer-based H∞ controller, and the system will switch to passive state with low damping at high frequency based on the dominant frequency of the vibration. In order to validate the effectiveness of the proposed friction observer, the Bouc-Wen friction model is selected to describe actual seat suspension friction, and it is compared with the estimated friction by the observer. Experimental results show that the friction observer has similar performance and less computational complexity compared with the Bouc-Wen friction model. The effectiveness of the proposed hybrid controller is validated on a six-degree of freedom vibration platform with the bump and random excitation. This friction observer-based hybrid controller is helpful for the engineering application as it applies practically measurable variables as feedback and considers the performance of the semi-active device in reality.