The agency picked up the account after a competitive pitch following a review process that kicked off in July.
Atelier will handle campaigns for the brand across North-West Europe - including the UK - and the Nordics.
In the past, Vitaminwater has worked with Droga5 on its global advertising. In the UK, the brand currently works with Exposure on its promotional activity.
Vitaminwater was a worldwide partner of London 2012, where it launched a limited-edition flavour, i-create. The new flavour was unveiled at an opening ceremony with a special performance by the brand's London 2012 Olympic ambassador, Jessie J.
The pop singer launched the first in a series of co-curation projects with Vitaminwater in September 2011.
Leo Burnett Group declined to comment.Follow @SaraKimberley