Initiative already handled smaller markets in Holland, Mexico and Spain for Burger King, and will now add to its portfolio Germany, Sweden and the UK.
Initiative beat incumbent Carat and MindShare, who formed the shortlist of agencies drawn up in January. Aegis-owned Carat had handled the UK and German part of the business since it was handed the account without a pitch in 2000. The Swedish business was managed by Mediaedge:cia.
Gillian Smith, Burger King's global senior director of media and interactive, said: "Appointing Initiative in six of our key markets will enable us to build on our innovative approach to media buying and planning. We are looking forward to bringing its expertise, particularly in the area of digital marketing, to the UK, Germany and Sweden."
Burger King announced the review at the start of December. The company sought to achieve greater consistency and cost efficiencies by consolidating the five European territories as well as Mexico into one account.
The fast-food giant initially drew up a longlist of agencies which also included Starcom Mediavest and Universal McCann.
Burger King spends between £10m and £15m annually in the UK, its second-biggest market outside the US. The pan-European media account is thought to be worth £30m.