A successor has yet to be announced.
"I have mixed emotions about the move, but I leave a team in great shape. I've loved my three years here, but I'm excited to be joining the birthplace of a network with which I have spent 11 years of my career," said Rebelo.
Rebelo has presided over an eventful period for Saatchi & Saatchi Singapore. During his tenure, the agency has won new clients including UOB, Sony Ericsson, Tiger Beer and ESPN, and was the 13th most awarded agency in the world in 2007, according to the Gunn Report.
Last August, Rebelo promoted Richard Copping to creative director and brought in Andrew Petch from Saatchi & Saatchi London, as associate creative director, following the departure of prolific award-winner Jagdish Ramakrishnan.
In January, he hired Nathan Hackstock and Simon Lazenby from Clemenger BBDO and M&C Saatchi Melbourne, respectively, to add much-needed steel to the agency's digital offering.
Rebelo added: "I'm joining an agency going through a lot of change, and will be teaming up with an inspirational leader [Robert Senior, CEO of the Saatchi & Saatchi/Fallon Group, to whom Rebelo will report]. It was too good an opportunity to say no to."
Saatchi & Saatchi London was drawn closer together to sister Publicis Groupe agency Fallon last year, forming SSF Group, in an attempt to revive the fortunes of the ailing Charlotte Street office.
Saatchi & Saatchi London has endured a troubled few years that have seen it lose control of a chunk of globally-aligned client Toyota, an account which, coincidentally, Saatchi & Saatchi Singapore relinquished last week.
Rebelo moved to Singapore in 2004 from Saatchi & Saatchi Australia, where he was general manager. He has also had a stint at Saatchi & Saatchi New Zealand.