The globe trotting continued in 2015. Mowlem raced in the United Sportscar Championship/North American Endurance Championship in the United States for BAR1 Motorsports in the Prototype Challenge category, driving an Oreca. Mowlem qualified on the class pole for the Rolex 24 at Daytona and finished second. He qualified on the front row for the Petit Le Mans race at Road Atlanta before finishing third in the race. Mowlem also competed in a 12-hour race at Abu Dhabi in a Ferrari 458 GT3.