He made his debut in the Grand Prix season on 4 August, in Hinterzarten, where he finished 7th in the team competition (with Tom Hilde, Lars Bystøl and Roar Ljøkelsøy).

The World Championship started dreadful for Jacobsen, falling from a bronze medal to 17th place after 86,5 m in the final round in the normal hill event.

Yet again he placed third after the first round at the large hill event, winning the bronze medal after the race's cancellation.

After winning a silver in the team large hill event Jacobsen won altogether two medals at the FIS Nordic World Ski Championships 2009 in Liberec.

He eventually won his sixth world cup victory in ski flying hill in Oberstdorf on January 31.