The team said his contract has an average annual value of $900,000.
Simmonds played in 38 regular-season games with the Maple Leafs this season, posting seven goals and two assists. He had an assist in seven playoff games as the Leafs lost to the Montreal Canadiens in the first round after holding a 3-1 series lead.
The Toronto native has 258 goals and 250 assists in 947 regular-season games with the Los Angeles Kings, Philadelphia Flyers, Nashville Predators and Maple Leafs. Simmonds has eight goals and 14 assists in 51 playoff games.
He was selected in the second round of the 2007 draft by Los Angeles.