Stastny's father, Peter Stastny, wore that number during his stellar NHL career, who played with Quebec, New Jersey and St. Louis from 1980 to 1995.
Defenceman John-Michael Liles gave No. 26 to the younger Stastny and took No. 4. The players were to don their new numbers for the first time in a game Saturday night against the Montreal Canadiens.
"I don't think numbers are a big issue, but it's that icing on the cake, that special touch to have the same number I wore my whole life and that my father had when he played in the NHL," said Stastny, a 21-year-old rookie forward.
"I feel grateful to have (Liles) as a teammate. He's one of the guys I look up to and the fact that he came up to me and asked me if I wanted the number speaks volumes about him."
Before making the offer, the 25-year-old Liles cleared it with one of his boyhood idols, former Avs defenceman Rob Blake. No. 4 became available when Blake signed with the Los Angeles Kings this summer.
"Giving up the number to Paul Stastny is the right thing to do," said Liles. "It's a family number.
"He deserves it. He worked hard to make this team and he's going to be part of this team for years to come."
Liles always wore No. 4 before he joined the Avalanche out of Michigan State University for the 2003-04 season. When the Zionsville, Ind., native went to his first Avs camp, he was given No 26 and kept it.
"If Stastny wasn't here, I would have stayed with No. 26," he said.
Paul is the second of Peter Stastny's sons to reach the NHL. Yan Stastny, 24, wears No. 43 for the Boston Bruins. Both were born in Quebec City.
Peter Stastny was named to the Hockey Hall of Fame in 2000 after producing 450 goals and 789 assists in 977 regular season games.
Most of his career was spent with the Quebec Nordiques, who moved to Colorado in 1995 long after Stastny had been traded away. He joined Quebec in 1980 after defecting from former Czechoslovakia with brother Anton and, later, his older brother Marian.
Peter Stastny has been a member of the European Parliament for Slovakia since 2004.