Duchene, 22, has 82 goals and 111 assists in 266 games with the Avalanche.
Ryan O'Reilly is expected to move to wing given the Avalanche's depth down the middle.
That depth could last a while with Duchene signed through 2018-19.
"Matt already is and will be a big part of our team's nucleus for the long term," Avalanche executive vice-president of hockey operations Joe Sakic said in a statement. "We all felt that it was important for us to secure his rights for several seasons. With his great skills, speed and character, he represents the identity we want the Avalanche to be."