The Ghana international will return to Norway, where he spent eight seasons with Stromsgodset prior to moving to Major League Soccer.
The Portland Timbers announced the transfer of goalkeeper Adam Kwarasey on Monday to Rosenborg BK in Norway's top division.
Kwarasey, who joined the club prior to the 2015 season, tore a ligament in his hand in April, and the stellar play of backup Jake Gleeson made the Ghana international expendable.
“On behalf of the Timbers, I would like to sincerely thank Adam for his major contributions to the club, both on and off the field, and for his instrumental role in helping the Timbers win their first MLS Cup," general manager and president of soccer Gavin Wilkinson said in a club release.