A V-shaped hybrid mass damper has been developed with a view to reducing the vibration induced by wind or earthquake excitation on a 230m high-rise building. The passive pendulum mechanism comprised of a Vshaped sliding mass is combined with the active control of the mass movement driven by a servo motor, and the mechanical system has been further refined for compactness and easy operation of tuning the natural frequency. The high performance of the device has been verified by numerical analyses and experimental tests conducted in a laboratory prior to its installation in the building concerned.