Arndt rode for between 2010 and 2012, before joining the team for the 2013 season. He achieved his first professional victory at the 2013
Arctic Race of Norway, winning the third stage, en route to finishing third overall behind
Thor Hushovd and
Kenny van Hummel. Arndt also won the young riders classification at the event, as the best-placed rider under the age of 25. The following year, he took his first win at the
UCI World Tour level, winning stage three of the
Critérium du Dauphiné in a sprint finish. In 2016, Arndt won the final stage of the
Giro d'Italia, his first
Grand Tour stage win. In early 2017, he won the
Cadel Evans Great Ocean Road Race, a one-day race on the World Tour. In June of the same year, he was named in the startlist for the
Tour de France, which was his first time competing in the race. He notably finished second on stage 19. His success at Grand Tours continued after a relatively uneventful 2018 season, winning stage eight of the
2019 Vuelta a España. He was part of the winning team in the
mixed relay event at the
2021 UCI Road World Championships in September. The month prior, he also won a stage of the
Tour de Pologne. After ten years with and its subsequent iterations, Arndt signed a two-year deal in August 2022 with , starting from the 2023 season. ==Major results==