A source close to the business said she resigned because of fundamental differences over marketing strategy with global marketers. It is not known if she has a job to go to.
Diageo sealed the sale of the business to Texas Pacific Group, Bain Capital and the venture capital arm of Goldman Sachs yesterday morning (Tuesday) for £945m ($1.5bn).
Joseph was head of marketing at Marks & Spencer before joining Burger King in September to replace Philip Almond, who opted to stay with Diageo.
Joseph arrived shortly after Delaney Lund Knox Warren was handed its creative account. It is not known if DLKW will be affected by reports that Burger King is to review its $300m US ad work.