No financial terms were disclosed, but TSN reported the contract is worth $4.3 million, an average annual value of $2.15 million.
"Zadorov is a big, young, physical defenseman who was starting to emerge as one of our top [defensemen] before his injury last season," general manager Joe Sakic said. "He's an important part of our blue line and we expect him to log big minutes this year. We are excited to have him under contract."
Zadorov, 22, who was a restricted free agent, had 10 assists in 56 games for the Avalanche last season. He was acquired by Colorado as part of the trade that sent center Ryan O'Reilly to the Buffalo Sabres on June 26, 2015.
"I think it's important for our team to get it done," Avalanche coach Jared Bednar said. "He played an important role on our team last year. I think it was a growth season for him. You look at our back end and where he has potential to go, we're excited about getting him done and getting him in here as soon as possible."
Selected by the Sabres with the No. 16 pick in the 2013 NHL Draft, Zadorov has 28 points (four goals, 24 assists) in 145 NHL games during four seasons with Buffalo and Colorado.
