Philipsen, winner of stages of the U23 Giro d'Italia and back-to-back overall titles at the Triptyque des Monts et Chateaux, was second in the U23 Tour of Flanders in 2017 and fourth in the U23 Paris-Roubaix this year.
He was in high demand after winning a stage in the Tour of Utah in Salt Lake City this season.
The Belgian is the latest from Axel Merckx's Hagens Berman Axeon development squad to move directly to the WorldTour, following in the steps of Rui and Ivo Oliveira, who also signed with UAE Team Emirates, Sean Bennett (EF Pro Cycling), and Will Barta (CCC). Other notable graduates from the programme in recent years include Logan Owen (EF-Drapac), Neilson Powless (LottoNl-Jumbo), and Tao Geoghegan Hart (Team Sky).
"It's a great honour to join UAE Team Emirates, I'm sure that this team will be the best possible way for me to develop my young career," Philipsen said.
"I sensed right away the faith that the whole team has in me, I think I'll be able to benefit a lot from this team project to show my best in the next years."