The German club informs about the transition in its media channels Thursday.
– It is the right step for me. I am looking forward to playing in the Bundesliga for such a big club, says Hansen-Aarøen about the transfer.
Manchester United reportedly wanted to keep the youngster, but Hansen-Aarøen is leaving the club on the last day of the transfer market.
The boy from Tromsø has not played a significant match for the Old Trafford club’s first team, but has many academy matches.
“We wish Isak the best of luck in the future,” United writes on its website.
The 19-year-old also has more than twenty matches for age-specific national teams.
He played seven games for Tromsø in the 1st division as a 16-year-old in the 2020 season.
Werder Bremen are currently in ninth place in the German top division.
Hansen-Aarøen becomes the second Norwegian player to sign for Werder Bremen on Thursday. National team goalkeeper Guro Pettersen joined the club’s women’s team a few hours earlier.