Lupul, who a source told ESPN.com will average $5.25 million per season, is now signed through the 2017-18 season. Sunday's deal comes a day after Lupul was picked as one of the Leafs' alternate captains.
"Joffrey has proven to be a dynamic offensive player and since joining our hockey club he has fit in extremely well with our team," Leafs general manager Dave Nonis said in a statement. "His alternate captaincy is well deserved and, by signing this extension, we look forward to him playing a large role with the Leafs for many years to come."
The 29-year-old played 66 games last season and ranked second on the team in goals (25), assists (42), points (67) and power-play goals (8). He had career highs for assists and points.
Lupul has 151 goals and 172 assists in 517 games with Toronto, Anaheim, the Philadelphia Flyers and Edmonton Oilers. The Fort Saskatchewan, Alberta, native was originally selected seventh overall by the Ducks in the 2002 draft.
Information from ESPN.com's Pierre LeBrun and The Associated Press was used in this report.