Lagace was waived by the Lightning on Friday, per CapFriendly.
Lagace signed a one-year deal with Tampa Bay on Sunday, per PuckPedia.
Lagace was demoted to the minors Monday.
Lagace was removed from the Lightning's main roster Saturday, per Erik Erlendsson of LightningInsider.com.
Lagace made 21 saves on 27 shots in two periods of play Thursday in a 9-3 loss to the Panthers. He was replaced by Hugo Alnefelt.
Lagace will protect the road goal in Thursday's game versus the Panthers, per the NHL media site.
Lagace made 27 saves in Tuesday's 5-4 overtime win over the Canadiens.
Lagace will be elevated to the active roster and get the starting nod against the Canadiens at home Tuesday, Joe Smith of The Athletic reports.
Lagace was recalled to the taxi squad from AHL Syracuse on Monday.
Lagace is one of three AHL goalies who could get game action Tuesday against Montreal.