ZenithOptimedia, the incumbent, was involved in the pitch process. It will continue to handle media for other Warner labels, including Warner Bros, East West and Rhino.
The7stars will work on Atlantic UK's domestic and international releases and will handle the media for pre-Christmas album releases from Bruno Mars, Ed Sheeran, Birdy and others.
Atlantic UK's other artists include Plan B, Rumer, Paulo Nutini, James Blunt and The Streets.
The7stars has extensive music industry experience, having worked for record labels including EMI, Ministry of Sound, Domino and Warp.
Gareth Jones, a director at the7stars, said: "It's a sector we love working in and we're really excited to be able to start working with a label such as Atlantic."