Sambrook, who announced in November that he was ending his 30-year career at the BBC, has been appointed as Edelman's chief content officer and global vice chairman.
In his new role, which he will take up in May, Sambrook will help clients produce written, video and audio content to tell their own story "in direct and engaging ways", a statement from Edelman said.
Sambrook will report to David Brain, Edelman EMEA president and CEO, and will be based in London.
He will also sit on the group's global executive committee, chaired by Richard Edelman.
Sambrook yesterday expressed his delight to be joining Edelman in a newly created senior role.
He said: "They are a company which I have long respected. Edelman's leadership with digital media and their work on trust and public engagement sets them apart and I'm greatly looking forward to helping to develop their content production and their approach to crisis and issues management."
In addition to his new post, Sambrook will also assume responsibility for the firm's global crisis and issues practice towards the end of the year when the man currently tasked with that role, Mike Seymour, begins to stand down from his full time position.
During his time at the BBC, Sambrook was responsible for leading the corporation's international news services across radio, television and new media. He then announced on his blog last year that he was leaving to become a visiting fellow at the Reuters Institute for the Study of Journalism before taking up a new job outside broadcasting.
Sambrook took up his role as global news director in September 2004 after publication of the Hutton Report. Previously, he'd been director of BBC News.
As director of news he had been a key figure in the BBC's row with Tony Blair's Labour government over the dossier that set out the reasons for going to war with Iraq.
Fallout from the row led to the departures of BBC director general Greg Dyke and chairman Gavyn Davies.
In a 30-year-career at the BBC he has been deputy director of the news division, director of sport, a producer and programme editor on national TV news programmes and news editor BBC newsgathering.
His first job in the BBC was as a sub-editor in the radio newsroom. Before that he was a trainee journalist on the Celtic Press and South Wales Echo between 1977 and 1980.
Sambrook has been succeeded by Peter Horrocks who is combining the directorship of global news with his current role as director of the BBC World Service.
Taken from Press Gazette.