The agency, which already handles Mars’ media buying, will now handle the £10m Wrigley media buying business, previously held at WPP's MediaCom.
Today' decision ends a three month review process and follows the $23bn merger of the global confectionery giants Mars and The Wrigley Company last October.
Omnicom's OMD was also involved in the pitch but has not picked up any of the business.
Similar local market reviews are taking place across Europe and beyond, although each will be run separately and be independent of one another.
The UK account includes the £35m media buying business for Mars UK, which includes products such as Dolmio, Uncle Ben’s and Klix; the £20m media buying for Mars Confectionery, which includes chocolate brands Mars Bars, Snickers and Galaxy; the £15m Petcare business, which includes Cesar, Pedigree and Whiskas; and the £10m Wrigley media buying business held by MediaCom since April 2002.