The ruling was handed down Tuesday after Swayman and the team had a hearing Sunday. The Bruins chose a one-year contract instead of two.
Swayman, 24, is again expected to share duties in net with reigning Vezina Trophy-winning goalie Linus Ullmark. The two shared the William Jennings Trophy this past season for leading the NHL in goals-against average, as the Bruins set league records for wins and points.
Boston's success certainly played a part in the ruling, as Swayman's numbers from last season helped to improve his resume. But Swayman backed up Ullmark last season with just a $1.05 million salary cap hit.
Now, given Ullmark's $5 million cap hit for next season, and Swayman's award, the Bruins will now have more than $8 million tied into their goaltending situation, provided they keep both before opening night.
The Bruins avoided arbitration with depth forward Trent Frederic, signing him to a two-year deal worth $4.6 million. Frederic, 25, will count $2.3 million against the cap each of the next two seasons.
Swayman and Frederic are two young players staying with Boston in the aftermath of longtime center Patrice Bergeron announcing his retirement.
The Associated Press contributed to this report.