The agency beat undisclosed agencies in a pitch process managed by The Observatory International.
JWT will be responsible for developing a global brand platform for the brand and the account will be led out of its London office, working with local offices in specific markets.
The appointment marks the first time that Grolsch has had a centralised global agency. In the UK, VCCP and BMB have previously worked on the business.
Richard Ingram, global brand and innovation director at Grolsch, said: "The JWT team really pulled out all the stops and demonstrated their passion for the brand and an ability to translate big idea thinking across all major channels, including comms, trade, activation and digital."
Joseph Petyan, regional director, JWT Europe, added: "Words don’t express how delighted we are to be working with this unique and premium brand across the world. We very much look forward to partnering with Richard and his Grolsch team to elevate the brand again to the position it absolutely deserves."