The 22-year-old defenseman could have been a restricted free agent July 28. He scored 44 points (eight goals, 36 assists) in 44 regular-season games for the Avalanche this season and 10 points (two goals, eight assists) in 10 Stanley Cup Playoff games.
"I'm definitely fortunate that we were able to get this done," Makar said. "Very happy and couldn't be more excited.
"I know this is a team that has the potential to win and to win now, and you don't want to sacrifice or get in the way of any of that. Just tried to do something that would work for both sides and I think we came to a deal that obviously works for both of us."
Makar was a finalist for the Norris Trophy voted as the top defenseman in the NHL. He tied for the lead at his position in game-winning goals (three) and was fourth in power-play points (22). He finished second on Colorado in ice time per game (24:19) behind defenseman Devon Toews (24:46) and tied for first in takeaways (32) with Toews and forward Mikko Rantanen.
The Avalanche (39-13-4) won the Presidents' Trophy given to the team with the best regular-season record in the NHL. They swept the St. Louis Blues in the Stanley Cup First Round and won the first two games of the second round against the Vegas Golden Knights before losing the best-of-7 series in six.
"I have so much faith in the organization and in the program that I think a longer-term deal was something more suitable for me," Makar said. "Regardless what the years were, we just wanted to work that out. I definitely have faith in what the program is building, where we are now and where we are going to be in the future."
Makar won the 2019-20 Calder Trophy voted as the NHL rookie of the year, when he scored 50 points (12 goals, 38 assists) in 57 games. He has scored 94 points (20 goals, 74 assists) in 101 regular-season games and 31 points (seven goals, 24 assists) in 35 Stanley Cup Playoff games. His 94 points are the sixth-most by an NHL defenseman through 101 regular-season games behind Hockey Hall of Famers Harry Cameron (115), Mark Howe (112), Brian Leetch (99), Larry Murphy (97) and Phil Housley (95).
He is one of five defensemen in the past 50 years to be named an NHL First Team All-Star before his 23rd birthday (Erik Karlsson, 21 in 2011-12; Dion Phaneuf, 22 in 2007-08; Ray Bourque (19 in 1979-80 and 21 in 1981-82; Denis Potvin, 21 in 1974-75 and 22 in 1975-76).
Makar was the No. 4 pick in the 2017 NHL Draft
"A deal of this magnitude, both sides have to feel good about it moving forward," Avalanche general manager Joe Sakic said. "He's a superstar. He's one of the top defensemen in the League, if not the best. He'll be up for the Norris year in, year out. We're very fortunate that for the next six years we're going to have Cale here and hopefully helping us win the Stanley Cup."
Avalanche goalie Philipp Grubauer and forward Gabriel Landeskog are among pending unrestricted free agents. Grubauer was voted a finalist for the Vezina Trophy awarded to the top goalie in the NHL after going 30-9-1 with a 1.95 goals-against average, .922 save percentage and seven shutouts in 40 games (39 starts). Landeskog was named captain Sept. 4, 2012 at 19 years and 286 days, at the time the youngest in NHL history.
"Obviously we want all of us back, especially 'Landy' and obviously 'Grubby,' they're such key pieces to our team," Makar said. "Those are guys I would love to see back and hopefully the club can work out something with them. Everybody is equal in this sense in just making sure, hopefully, everybody gets the right deal and get it done at some point, hopefully before everything starts to funnel out."
NHL.com senior writer Dan Rosen contributed to this report
