The pitch was managed by Media Audits and was overseen by Ian Gallois, Wrigley's new media director for Europe, the Middle East and Africa.
It is thought the pitch was prompted by the merger of CIA with The Media Edge, which created a clash between Wrigley and The Media Edge's Colgate-Palmolive account.
The chewing gum market has been in a state of flux recently as competitors have attempted to steal share from the market leader, Wrigley.
Last August, Colgate-Palmolive launched a £13 million campaign for its Advanced Action Dental Gum, and it was recently reported that Cadbury Schweppes is embarking on a $2 billion bid for Adams, the chewing gum arm of Pfizer.
This prevented the Cadbury agency Carat, which handles the Wrigley account in several European markets, from pitching for the account in the UK.
MediaCom takes over responsibility for the account from the beginning of next month, reporting to the Wrigley marketing director, Gharry Eccles.
Eccles said: "MediaCom was appointed for its strategic planning, its creativity and innovation in communication and its client philosophy."
Wrigley's brands backed by advertising include Airwaves, Juicy Fruit, Extra and Orbit. Its new Xcite brand will also be part of MediaCom's brief.
Steve Allen, the MediaCom chief executive, said: "Wrigley is one of the most well-known brand names in the world. With such a large portfolio of products offering a range of benefits and the continued growth in the chewing gum market, this is a fascinating account to win and a relationship we look forward to developing."
There are suggestions that the Wrigley's win may rule MediaCom out of the current Mars planning pitch as it might be considered a competitive account.