In 2006 he was picked for one of the eight spots in the Norwegian World Cup team. He made his debut in the Grand Prix season on August 4, in Hinterzarten, where he finished 7th in the team competition (with Tom Hilde, Lars Bystøl and Roar Ljøkelsøy). On August 5, he was eighth; on August 14, in Courchevel, he was fourth; on August 24, in Zakopane he was seventh; on September 30, in Klingenthal, he was sixth; on October 4, in Oberhof, he was tenth. He was tenth in the Grand Prix, with 184 points.
Entering the FIS Nordic World Ski Championships 2007 in Sapporo, Jacobsen leads the overall Ski jumping World Cup standings. At those championships, he earned a silver medal in the team large hill. But he failed in the large hill competition, and finished 7th in the normal hill competition.
After the World Championships, Jacobsen has struggled to maintain his form. He failed to qualify for the finals in Lahti, finished 10th in Kuopio, and 14th in the first Holmenkollen cometition. Adam Malysz won all those races and therefor he overtook the lead in the World cup standings.
On August 9th 2008 Jacobsen married his girlfriend Birgitte Jacobsen.