Boasson Hagen soloed to victory on stage 19 of the Tour de France, successfully attacking from the breakaway in the final few kilometres. Boasson Hagen, along with Nikias Arndt, took the right side of a roundabout with only 2.2 kilometers remaining, whilst the remainder of the breakaway took the left. The right side of this roundabout ended up being shorter than the left and thus created a gap for the two cyclists. Boasson Hagen was then able to drop Arndt from his wheel to take the victory. This victory marked Boasson Hagen's only triumph at the 2017 Tour de France despite finishing on the podium 5 other times, on stages 7, 11, 14, 16 and 21.