Fleury made 46 saves for Chicago (22-30-9).
"Yeah, he was outstanding," said Blackhawks coach Derek King. "I don't know what else to say about this guy. When he's on like that, it's fun to watch. I don't want to say there were a lot of outside shots, they were easy shots to see, but he made some spectacular saves.
"First game against Boston (a 4-3 loss Thursday), I think we deserved better. Just the way it went. Tonight, I think they deserved better."
Linus Ullmark made 19 saves for Boston (37-18-5), which is 10-1-1 in its past 12 games.
Ullmark said he was inspired to match Fleury's play.
"It gets me a little fired up, obviously, because he's doing a tremendous job stopping pucks and he's playing with a lot of energy," Ullmark said. "And he's done it for all these years in the League. He's a great goaltender. That's it. But admiration, no. But afterwards now, if we were able to look at the game, I would say he was terrific tonight."
Patrice Bergeron gave the Bruins a 1-0 lead at 4:43 of the third period. He batted the puck out of midair and scored on the 40th shot against Fleury.