Stuart's goal broke a tie a period after brother Colin scored his first NHL goal for Atlanta, and the Bruins ended a six-game skid with a 5-2 victory over the Thrashers on Monday.
"It was nice," Mark Stuart said. "He one-upped me earlier, so I had to do it."
Boston's first goal of the game -- a power-play score by Dennis Wideman -- was the team's 18,000th, making the Bruins the second NHL team to reach that mark. Montreal has 18,886.
"Maybe Boston Bruins' trivia one day," Wideman said.
Phil Kessel and Matt Lashoff added insurance goals in the third for Boston. P.J. Axelsson also scored for the Bruins, 0-5-1 in their previous six games. It was their worst stretch since they ended last season 0-6-0.
Colin Stuart's first NHL goal came in just his second career game. Bobby Holik also scored for the Thrashers.
"Getting that first NHL goal is exciting, but it would've made it more exciting if we came out of here with a win," Colin Stuart said.
Atlanta led 2-0 after the first period before Boston scored three in the second.
"I think we stopped trying so hard and stopped doing the easy things and cost ourselves a game," Atlanta goalie Kari Lehtonen said.
With the score tied 2-all, Mark Stuart fired a slap shot from the top of the left circle that got past Lehtonen to move Boston ahead 9:40 into the second period.
"I think we just decided to play," Boston coach Claude Julien said. "That's what my message was to them right after the first period."
Kessel and Lashoff's goals both came on power plays in the opening 6:37 of the third. Boston was 3-for-4 on the power play.
Kessel scored off the rebound of Andrew Ference's shot from the point 2:05 into the final period. Lashoff's slap shot from the left point beat Lehtonen inside the far post.
Bruins goaltender Tim Thomas made 28 saves.
Thrashers' left wing Ilya Kovalchuk, the NHL's leader with 32 goals, was held to one assist.