The team's career scoring leader will be honored before a Feb. 11 game against Montreal when his No. 13 is raised to the rafters. Sundin will be the 18th player to have a banner raised in his honor by the Maple Leafs.
Only Bill Barilko's No. 5 and Ace Bailey's No. 6 are officially retired. The rest of the numbers can still be worn by current players -- although no one has donned No. 13 since Sundin.
The club made the announcement midway through the first period of a 4-3 win over the Pittsburgh Penguins on Saturday night.
It's been nearly four years since Sundin last wore a Maple Leafs jersey, but the 19,526 in attendance let him know how revered he remains in the city. Fans gave the former team captain a standing ovation that lasted the entire TV timeout.
"I don't know what to say," the 40-year-old Sundin said. "Once you retire you get a chance to reflect more on your career, where you've played and what it meant to yourself.
"To get a chance to represent the Leafs for all the years that I did and play in a city like this, it's a huge honor."
A smiling Sundin looked overwhelmed by the crowd's reception after the announcement.
"To be recognized in that way, you're never going to feel like you deserve it," he said. "I'm just happy to be mentioned in the same breath as Borje Salming, Darryl Sittler and all these great legends of the game of hockey."
It was Sundin's first time back in the arena since retiring in 2009. The Swede played for the Maple Leafs from 1994-08, amassing 987 points, including 420 goals, in 981 games.
When he joined the Maple Leafs after being traded for Wendel Clark at the 1994 draft, Sundin didn't know what to expect coming to hockey-mad Toronto.
"It took me a while to get used to that," he said. "Coming to a city where people care about the game and everybody's involved, it's something I enjoyed. It's great to be in a city where people really care about your team."
"It's tough to explain to people. You have to come here to see it. You can't explain it to people in Sweden or anywhere else in the hockey world. You have to come here and live it."
Sundin now lives in Sweden with his wife, but he still considers Toronto his second home.
"It's like coming home every time and that's not going to change. I'm just happy to have this great ending. It's been such a big part of my life and to have my relationship with the Leafs and this city, for the rest of my life, it's going to be something I'll cherish for sure."
Sundin won an Olympic gold medal in 2006 with Sweden, but he was never able to bring that elusive Stanley Cup to Toronto.
"I played almost 20 years and made it to the conference finals twice, but of course you want to win the Stanley Cup," said Sundin, who had 70 points in 77 playoff games for the Maple Leafs. "But saying that, my career has given me so much.
"The two runs in the conference finals (1999 and 2002) -- those were great memories. But any time in the playoffs, here, it's the only city where you win one playoff game in the first round and everyone is celebrating like you'd just won the Stanley Cup. It's something else and it's very special. I don't think you get that anywhere else in the world."
Sundin chose No. 13 because Joe Sakic had No. 19 when Sundin was drafted first overall by the Quebec Nordiques in 1989. Sundin went back to the number he wore in juniors, 13. He also was born on Feb. 13.
"Everything I have I have to thank the people of Toronto, the fans and the franchise," he said.