In 2015, Kristoff had a very good start to his campaign by getting three stage victories at the Tour of Qatar, grabbing the points classification jersey in the process. He celebrated another stage victory soon afterward at the Tour of Oman. On 1 March, he was outsprinted by Mark Cavendish and finished in second position at Kuurne–Brussels–Kuurne. He earned another sprint victory at Paris–Nice, while he was preparing himself for Milan–San Remo. He was looking for a repeat victory at that race, but John Degenkolb had the better of him in the sprint finish and he settled for second position. Still in the month of March, he went on to finish just shy of the podium in E3 Harelbeke, taking fourth place. He then participated in the Three Days of De Panne, where he was part of a six-man breakaway on the first stage and won the sprint of the small group, while being lead-out by his teammate Sven Erik Bystrøm. He repeated the next day, this time using a bunch sprint to propel himself to victory. Kristoff also won stage 3a, a bunch sprint where he very slightly edged André Greipel by 0.0003 seconds. With the bonus seconds awarded to him, he won the general classification too after finishing third on stage 3b, a short individual time trial. In April, Kristoff won the cobbled monumentTour of Flanders, the main goal of his spring season. With some remaining, Niki Terpstra attacked and only Kristoff went with him. The duo got a lead of 30 seconds with the remains of the lead group unable to catch them. Kristoff beat Terpstra in the two-man sprint, to take his biggest win up to that point. Three days later Kristoff won the sprinters' semi-classic Scheldeprijs, becoming the first rider to win the Three Days of De Panne, the Tour of Flanders and Scheldeprijs in the same season. Kristoff came in tenth at Paris–Roubaix, and then took a break from racing. He came back at the Tour of Norway, where he finished eighth overall while taking two stage successes. Shortly after, he participated in the Tour des Fjords where he dominated the sprints again by amassing three stage victories, the points classification jersey and a ninth overall position. He also won the seventh stage of the Tour de Suisse ahead of Peter Sagan. Sagan got out of Kristoff's slipstream to try to out-sprint him in the closing stages, but to no avail.
2016 season
In 2016, he started his season with a hat-trick of stage wins at the flat Tour of Qatar, finishing in second position in the overall classification to Mark Cavendish.
Later in August 2017, it was confirmed that Kristoff had signed an initial two-year deal with starting from the 2018 season. He moved there with fellow Norwegian Sven Erik Bystrøm.
2018 season
Kristoff started his first season with his new team at the Dubai Tour. He followed this up with appearances at two more stage races in the Middle East. At the Tour of Oman, he took victory in the sixth and final stage. His second victory of the season came of the opening stage of the Abu Dhabi Tour. He won the last stage of the Tour de France in a sprint on the Champs-Élysées in Paris.
2019 season
In June 2019, Kristoff extended his contract by a further two years, to the end of the 2021 season.
