Bergesen will receive an $800,000 salary this year rather than his request for $1.2 million. Arbitrators Robert Herzog, Mark Burstein and Elizabeth Neumeier made their decision Thursday, a day after hearing arguments.
Bergesen was 2-7 with a 5.70 ERA in 12 starts and 22 relief appearances last season, when he made $434,000.
Baltimore went to a hearing for the first time since beating pitcher Rodrigo Lopez in 2006.
Orioles outfielder Adam Jones is among 11 players still scheduled for hearings.