The forward, who could have been a restricted free agent after this season, had an NHL career-high 76 points (41 goals, 35 assists) last season, his second with the Blackhawks after they selected him in the second round (No. 39) of the 2016 NHL Draft. The 21-year-old has 128 points (69 goals, 59 assists) in 164 NHL games.
"It's nice to get it done this year," DeBrincat said. "It shows they have confidence in me. I didn't want to be waiting around like a lot of the [restricted free agents] this year ... I think from the start I wanted to get it done early and not really worry about it. When they came to offer us a contract it was pretty easy decision to make, get it done now and just focus on the season."
Chicago general manager Stan Bowman said the Blackhawks' feelings were mutual.
"It's great news for everyone," Bowman said. "Congrats to Alex, first off. He deserves it. What a great first two seasons he's had. I think he's just scratching the surface. To score 40 goals in his second year, and I think he's got a lot of great years ahead of him. ... I think it was a deal that works both for us and for him and rewards him for his performance, and it sets us up well for where we're headed.
"It is nice to have it out of the way for now and certainly starting the season, we can all focus on getting off to a good start. But it didn't have to happen now. I think there's a lot of time until his first deal was expiring. So from that perspective, it just worked nice, and happy for him."
DeBrincat (21 years, three months) became the second-youngest player in Blackhawks history to score 40 goals in one season. Jeremy Roenick (21 years, two months) scored 41 in 1990-91.
The Blackhawks open their regular season against the Philadelphia Flyers in the 2019 NHL Global Series at O2 Arena in Prague on Friday (2 p.m. ET; NHLN, SN360, NBCSP, NBCSCH, NHL.TV).
NHL.com staff writer Tracey Myers contributed to this report
