Grayling and Landmark will manage the tour’s global reputation, promote its tournaments to golf fans and market its network of properties.
The two agencies have been working together for the client since 2012, when they were appointed to manage communications for the 2014 Ryder Cup, for which the European Tour is responsible when played on European soil.
Hubbed from Grayling’s Edinburgh office but with contributors throughout the world, the account will involve teams in London, Bristol, Dublin, Lisbon, Istanbul, Dubai and Shanghai.
Despite its name, the tour has become increasingly global, having been played in 41 countries across six continents, including China and Dubai.
Rumours that it could join with America's PGA Tour were fuelled last year when European Tour CEO George O'Grady told the Wall Street Journal the sport was "evolving towards" a global competition.
Tim Hunt, marketing communications director for the European Tour, said: "We have enjoyed a superb relationship with Grayling and Landmark Media, which have exceeded our expectations with the Ryder Cup contract. They have a real understanding of our objectives and they represent us with professionalism and passion.
"It was a natural process to ensure we could also benefit from that advice and guidance right across the European Tour. We operate on a global stage and Grayling’s international network closely aligns with our needs. We expect that contribution to aid our push to engage golf fans while increasing the commercial impact of the tour around the world."