The 33-year-old Czech missed most of the 2016-17 campaign after undergoing hip surgery. Hemsky had seven points (4-3) in 15 games with the Dallas Stars last season.
"I’m training at 100 per cent and I’m back to 100 per cent right now," Hemsky said on a conference call. "So I’m sure I’ll be ready for the season and for training camp. I’m excited for that."
Hemsky made his NHL debut with Edmonton in 2002-03 and spent over a decade with the Oilers.
In 838 career regular-season games, Hemsky has 174 goals and 398 assists for 572 points. He has 21 points (7-14) in 43 playoff games.
"It happened really quick," Hemsky said of the signing process. "I had to make a choice so I did today and signed with Montreal. It will be a good opportunity for me."