Lindholm scored 38 seconds later on the power play to put the Bruins back ahead 2-1 at 7:41 with a backhand shot off a pass from Pastrnak on the rush.
Swayman made a pair of saves with Thompson pulled for the extra skater before Geekie scored into an empty net at 19:02 for the 3-1 final.
“I thought we play a solid game,” Washington captain Alex Ovechkin said. “We have lots of chances, but obviously we didn’t score on our chances on the [power play] and at the end we still have a chance to tie it.”
The Bruins went 1-for-2 on the power play; the Capitals were 0-for-5.
“That’s something we need to build on right away and take pride in,” Swayman said of the penalty kill. “I think we did a great job just sticking to our routs, making great reads, blocking shots when needed. That’s something you really want to see early on.”
NOTES: The Bruins are 11-3-0 in their past 14 season openers. … Pastrnak (nine goals, eight assists for 17 points) passed David Krejci (14 points) for the third-most points in season-opening games in Bruins’ history. The only players with more are Ray Bourque (30) and Johnny Bucyk (17). … Washington has lost its past four season-openers. … The Capitals wore “26 POPS” stickers on their helmets in honor of forward Nic Dowd’s father, Alan, who passed away last week.