NHL Player Safety announced the ban Wednesday night following an in-person hearing with Marchand earlier in the day.
Marchand was already suspended once this season, for three games, when he slew footed Oliver Ekman-Larsson. This will be the eighth suspension of Marchand's career and the longest, following two five-game bans previously.
That Marchand is a repeat offender factored into NHL Player Safety's decision to make this a six-game suspension.
"Players who repeatedly violate league playing rules will be severely punished for each new violation," Player Safety noted in a video, citing terms of the NHL/NHLPA collective bargaining agreement. "Marchand has been suspended seven times, and fined five times previously."
This incident between Marchand and Jarry occurred during Pittsburgh's 4-2 victory over Boston on Tuesday. The Bruins were trailing by two with less than a minute to play in regulation, and Jarry had just smothered a puck. Marchand was in the vicinity, and after it appeared that Jarry said something to Marchand, the Bruins winger took a swing at him.
Marchand's punch unsurprisingly drew several of Jarry's teammates into the fray. Linesman Andrew Smith also was involved and tried to get Marchand off the ice and away from Jarry, but Marchand escaped Smith long enough to hit Jarry's mask with his stick.
The dustup earned Marchand a five-minute match penalty for attempt to injure and a two-minute call for roughing. Since the melee took place in the game's final minute, it was automatically subject to NHL review.
Bruins coach Bruce Cassidy said he watched a replay of what happened after the game and saw an obvious "lack of discipline" on Marchand's part in the moment, but Cassidy also noted that something had clearly sparked Marchand's anger toward Jarry.
"It looked like some words were exchanged," Cassidy said. "I don't know if there was an incident at the end of the second period that precipitated it. I was in the room, so I don't know. Someone said that. Still, you've got to have better discipline at the end of the day. Brad's a leader on our team. He needs to control his emotions in that situation."
If Jarry was bothered by Marchand's behavior, he didn't let on during a postgame news conference in which he downplayed the incident.
"I think it's just the heat of the moment," Jarry said. "Everyone's battling hard out there, and he's just trying to get the puck to the net ... it's part of the game, and [what happened] stays on the ice."
Marchand leads the Bruins in scoring this season with 21 goals and 49 points. Losing him under any circumstance would be a blow, but especially now, when the Bruins also are dealing with an upper-body injury to captain Patrice Bergeron, suffered in that same Tuesday game. Bergeron will miss Boston's tilt against the Carolina Hurricanes on Wednesday, and there is no timetable for his return.