Active vibration control is a revolutionary technology to deal with vibration issues in floors. These issues range from (1) resolving vibration problems that arise in service, (2) upgrading existing floors for change of use, and (3) delivering a future generation of floor structures that are increasingly sustainable and yet still exhibit excellent vibration characteristics. Following nearly two decades of fundamental academic research, the CALMFLOOR active vibration control technology has been brought to market and has been successfully deployed in a range of projects in the UK, Europe and North America. It is also planned for adoption in a wide range of retrofit and new-build applications. This paper presents an introduction to the active mass damping technology, and presents a real-world case study of successful application. Problematic vibrations of a leisure facility were resolved very quickly, with reductions in magnitude of 76% being observed and complaints from other tenants in the building being eliminated. No structural intervention was required, which would have been extremely costly and disruptive to the client.