The WPP agency clinched the account following a final round of pitching 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 agency's Asia-Pacific's chairman and CEO Mike Amour, confirmed the win. He 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."
Mok commented: "We are very excited about this win and as a Hong Kong-born Chinese, I am proud to play a part in promoting Hong Kong as a destination for overseas travellers."
The account was previously handled for nine years by DraftFCB, which resigned the business in late 2007.
