Modem high rise construction materials and techniques have led to the proliferation of tall buildings that are lightweight, flexible, and possess low inherent damping. These structures are often susceptible to excessive wind-induced motions, which may cause discomfort for occupants on the upper storeys. The tuned sloshing damper (TSD) can be employed as an affordable, efficient, and simple means to mitigate building motion. A TSD consists of a tank located near the top of the structure, which is partially filled with water. As the building sways under wind action, the water within the tank will slosh. When properly designed, the force imparted to the structure by the sloshing water will counteract the wind loading, significantly reducing the building's motion. In traditional multi-tank TSD installations, all tanks are tuned to the natural frequency of the structural vibration mode being targeted. More recent research has shown that improved performance can be achieved if the tanks are set to slightly different frequencies near the structural mode being controlled, instead of having all tanks identically designed. This study first overviews a simple model to describe the response and performance of multiple tuned sloshing dampers (MTSDs) with frequencies distributed near the structural frequency of the targeted mode. Using this model, the advantages of considering the MTSD system are illustrated. The performance of the MTSD system is then demonstrated using full-scale measurements of a high rise building located in Toronto, Canada. To the authors' knowledge, this is the first building in the world equipped with this type of efficient MTSD system.