The 6,000-strong South Korean agency group, which unveiled the Iris deal in November, has created the role as part of a global business development push.
Malm Hallqvist, who has been global chief growth officer at McCann for almost four years, will continue to be based in London and will report to Cheil’s global chief operating officer Michael Kim.
She co-founded Propaganda, an advertising agency, in 1997, which later sold to McCann.
Kim said: "Cheil is at a really important chapter in its history and there is no better time than now to have a new global chief growth officer on board.
"Lotta, a hugely charismatic, engaging and passionate professional, has helped agencies build growth and drive business development over the past 15 years."