He also was an assistant for Sweden at the 2026 Winter Olympics.
Alfredsson played 1,246 NHL games with the Senators and Detroit Red Wings from 1995-2014. He spent 17 seasons with Ottawa, where his 426 goals, 682 assists and 1,108 points are team records.
He became the first Senators player from the modern franchise to have his number retired in 2016, and he was inducted into the Hockey Hall of Fame in 2022.
"One of the first moves we made after taking over the franchise was bringing Daniel Alfredsson back into the fold as an assistant coach in December of 2023," Senators owner Michael Andlauer said in a statement. "I quickly learned that 'Alfie' embodied all the characteristics of what it meant to be an Ottawa Senator.
"While I wish he wasn't joining an arch rival, Alfie is forever an Ottawa Senator and the door will always be open for his return. He has done so much for our organization and community and he has my full respect."
John Gruden and Brad Werenka were also hired by the Maple Leafs on Tuesday as assistant coaches.
"I'm incredibly excited to add Daniel, John and Brad to our coaching staff," said Toronto coach Jim Hiller, who was hired June 17 to replace Craig Berube. "Daniel's experience, leadership and understanding of the game speak for themselves. John has established himself as one of the top coaches in the American Hockey League and played an instrumental role in leading the Marlies to a Calder Cup championship last season. Brad brings a unique combination of NHL experience, player development and expertise in performance analytics. Together, they'll be outstanding additions to our team."
