The three-year contract will see Grey handle advertising across 18 global markets.
Grey will partner with MindShare, which will handle media planning and buying.
While the HKTB marketing budget is HK$331 million (US$42.4 million) for the next year, the above-the-line ad spend is believed to be a small fraction of this budget.
Danny Mok, GM of Grey Hong Kong said: “We won the account because of our strategic and creative capatibility, strong international and integrated team, and support from our global networks.”