Donato tied it 2-2 at 2:02 of the third, shooting in his own rebound on a 2-on-1 after Caleb Jones slid into Fleury and knocked him down.
"It's very relieving," Donato said. "I've said this quite a bit, we're waiting for a win for a long time and sometimes things get tough that you kind of forget what it feels like. Things happen like that. Things are great, and hopefully we can get some steam off of that and keep rolling."
Fleury made two saves on Jared McCann to keep the game tied. He got across his crease and made a lunging glove save on the forward's one-timer during a power play at 7:33 before stopping him with his blocker on a penalty shot at 13:34.
"It's unbelievable sometimes, and today I was just sitting on the bench watching the replay," Kubalik said. "What is he doing up there? I'm expecting it's already going in and somehow he always makes the save, so he gave us the point."
Alex Wennberg had a chance to win it late in overtime for Seattle, but his shot from the slot hit the crossbar with 3.9 seconds remaining.
"We earned it today, going through the 60 minutes, through overtime and then just poise to make plays with the guys in the shootout," Hakstol said. "… The win tonight comes from the full body of work to the small areas of the game."
Kubalik gave the Blackhawks a 1-0 lead at 12:06 of the second period. After Erik Gustafsson poked the puck away from Donato, the defenseman sent a stretch pass to Kubalik, who beat Grubauer blocker side on a breakaway.