The two clashed during a one-on-one drill. Both dropped their gloves and their teammates backed away to let them go at it for a few seconds before Josh Gorges and others stepped in to stop it.
No big punches landed and neither player was hurt. Both stayed on the ice as practice resumed.
"It's nothing personal between me and P.K. It's about the team and to realize we have to start playing as a team," Plekanec said. "Those things happen."
"It's not the first time. It happened between some other guys. That's what happens during the course of the year when things are not going well. I wouldn't say it's a frustration thing, it's just that we realize we need to be better," he said.
The Canadiens (14-18-7) went 1-5-0 on a road trip that ended with a 3-2 loss in Florida on Saturday. They have one win in their last eight games. Their next game is Wednesday at home against Winnipeg.
Subban has exchanged angry words with teammates before, but it was unusual to see Plekanec lose his temper.
Gorges said it perked up the practice.
"You (reporters) will make a lot more of it than it was and you'll talk about why it happened and who it was, but the next drill, (Chris Campoli) had a good hit, guys got fired up, the intensity rose and we had a good practice out of it," he said.
Subban was scratched from a game last week after making costly errors in consecutive games. Plekanec's production is down even though he still leads the club in scoring.
Subban was not available for comment. He was in the middle of a ruckus Saturday in Florida when Panthers forward Krys Barch was ejected for allegedly making a racial remark to the Montreal defenseman. The NHL has yet to announce whether Barch will be fined or suspended.
Canadiens veteran Mathieu Darche saw the fight as a positive.
"It shows guys care," he said. "Trust me, I've been on teams where you see a lot more of those.
"For us it's not a story. We laugh about it. In the gym, P.K. and Pleky were talking. It's part of being a competitor. You'd rather see that than guys not giving a (darn). Guys aren't happy. We're losing and sometimes emotions get the best of you. There's nothing wrong with that."