Isobar has been tasked to develop the restaurant chain’s digital strategy "with an ambition of driving innovation in their digital communications".
Vizeum, Isobar UK’s sister agency, picked up the £60 million European media business for Burger King in November last year.
David, part of the Ogiilvy & Mather group, is Burger King's global creative agency. CHI & Partners handled the £9 million UK business up until the review in 2014.
Isobar UK's first digital campaign will launch towards the end of the year.
Nick Bailey, the chief executive at Isobar, said: "Burger King has a legacy of ground breaking work in the digital space.
"We are hugely excited to be working with them to continue that legacy and to be working with our partner agencies within Dentsu Aegis Network to deliver a truly integrated solution."