The review, called in May, saw Publicis-owned Starcom, Omnicom-owned PHD, Aegis agency Carat and a combination of The Seven Stars and Naked Communications originally pitch for the account.
The UK pitch was part of a wider, pan-European review that saw Starcom retain the business in continental European markets including France and Spain, and add Italy, Turkey and Greece to its remit. Universal McCann won the business in Romania. The business is globally aligned to Publicis Groupe.
Philippa Brown, the acting chief executive of PHD UK and chief executive of Omnicom Media Group UK, said: "We felt we were the right fit from the start. Cadbury wants to do things differently in the media space and so do we, as we are traditionally a pioneering agency."
Starcom had held the UK account since 2003.