Rask, 34, had stated at several points that it was essentially either a return to the Bruins or an early retirement, as he did not wish to play in a different city at this stage in his career.
The Finnish netminder went 15-5-2 with the Bruins in 2020-21, including 3 shutout victories. He posted a 2.28 GAA and a .913 sv% in his 24 appearances with the club last season.
The 560-game NHL veteran has been sensational throughout his NHL career, posting a career .921 sv% and a 2.27 career GAA. He is also the only goaltender in Bruins franchise history to amass 500 games.
Rask had been released from his PTO with the AHL's Providence Bruins earlier on Tuesday. No word yet on who will be sent down to the taxi squad, but since Jeremy Swayman is waivers-exempt, he figures to be the likely candidate, with Linus Ullmark working alongside Rask for the B's.