The WPP agency got the green light after a final contest against Publicis, Saatchi & Saatchi and DDB. Media planning and buying will be handled by MindShare.
Grey will handle the business on a three-year contract across 18 markets.
The Grey Asia-Pacific chairman and chief executive, Mike Amour, said: "It's a great win for Danny Mok (Grey Hong Kong's general manager) and his team. What's significant is that it was a total communications effort."
The account was previously with DraftFCB, which resigned it in late 2007 after nine years.