The 38-year-old is moving into the Maple Leafs' front office as a special assistant to general manager Kyle Dubas.
Spezza finished with 995 points (363 goals and 632 assists) in 1,248 regular-season NHL games, with 76 additional points (28 goals and 48 assists) in 97 playoff games.
The two-time NHL All-Star (2008, 2012) ranks in the top 100 on the NHL's career list for games played (tied for 96th), assists (80th) and points (94th).
He had 12 goals and 13 assists in 71 games this season, adding an assist in five playoff games.
"Hockey has been my life's work and to be able to come home to Toronto and bookend my playing career where it started was incredible," Spezza said in a statement. "To the fans -- in Ottawa, Dallas, Toronto and across the league -- your impact on the game is immeasurable. I'll never be able to replicate that feeling of stepping onto the ice to the roar of the crowd, but it is something I'll always remember. Thank you."
The eighth captain in Ottawa franchise history, Spezza ranks sixth in games played (686) and second in goals (251), assists (436) and points (687) through his 11 seasons with the Senators.
Spezza added veteran savvy to the Leafs during his time in Toronto, often playing a bigger role with the team off the ice than on it.
"It is difficult to describe just how much of a lasting and positive impact that Jason Spezza made in his three seasons with the Maple Leafs," Dubas said. "Jason's passion for the game of hockey, his desire to continuously push himself and his teammates to improve, as well as his capacity to make strong connections with all members of the organization, have been invaluable.
"Though today marks the end of his tenure with us as a player, it is a pleasure to have him join our front office to impart all that he has to offer."
Spezza represented Canada at four world championships (2008, 2009, 2011, 2015), three world junior championships (2000, 2001, 2002) and the Spengler Cup in 2012.