The agency has handled media for the Atlantic, East West and Rhino record labels for four years.
Starcom Mediavest Group was the incumbent and repitched for the account. The process was handled by 23 Media Audits.
Warner Music UK’s artists roster includes Biffy Clyro, Blur, Coldplay, Ed Sheeran, Lianne La Havas, Muse, Paolo Nutini, Plan B, Royal Blood and Rudimental.
Gareth Jones, a partner at the7stars, said: "We see this as a time of revolution with release dates moving to Friday, the rise of streaming and the launch of Apple Music. With these opportunities, I can’t think of a more exciting time to be working together."