Folin agreed to a one-year, one-way contract extension with the Canadiens on Thursday.
Folin had an even-strength assist and four shots in Tuesday's 8-1 win over the Red Wings.
Folin was traded from the Flyers to the Canadiens -- along with Dale Weise -- for David Schlemko and Byron Froese on Saturday, Frank Seravalli of TSN.ca reports.
Folin has played six games this month, posting zero points and a minus-3 rating.
Folin hasn't played since Nov. 24, as he's been a healthy scratch in each of the last 16 games.
Folin has six shots on goal, a plus-1 rating, 10 hits and nine blocks in the last five games.
Folin has one assist with a plus-4 rating and eight shots on goal in nine games this season.
Folin will dress for Saturday's home game against the Islanders, Bill Meltzer of NHL.com reports.
Folin signed a one-year contract with the Flyers on Thursday.
Folin marked 13 points, 167 hits and 106 blocked shots through 65 games in 2017-18.