Smarts Communicate London, whose Belfast-headquartered parent company is the fourth-largest consultancy in the UK with an HQ outside London, picked up the business following a four-way pitch.
The agency will focus on tailored communications campaigns for four Marriott brands: AC Hotels, Aloft Hotels (pictured), Element and Moxy.
The brief incorporates raising awareness of the brands’ "individual personalities" and driving hotel bookings through traditional PR, influencer outreach, social media and events.
"The proposal from Smarts truly understood our need for practical creativity and excelled with clever ideas that could be rolled out across multiple markets," Select Brands Europe director of communications Maria José Crousillat said.
Helen Rainford, managing partner of Smarts Communicate London, added: "This European brief was right up our street – allowing us to combine our global experience with best in class creativity. Each of the brands has such a distinctive offering so we’re delighted to be able to tell their unique stories."