The 31-year-old goalie, who was an unrestricted free agent, went 12-15-3 with a 3.01 goals-against average and .907 save percentage in 33 games (30 starts) with the San Jose Sharks last season.
The Maple Leafs also have goalies Frederik Andersen and Jack Campbell on their roster. Andersen is signed through the 2020-21 season, which is targeted to begin Jan. 1, 2021, and Campbell has two seasons remaining on his contract.
Signed by the Sharks as an undrafted free agent March 4, 2015, Dell is 48-34-12 with a 2.76 GAA, a .908 save percentage and five shutouts in 107 regular-season games and 0-1 with a 3.08 GAA and .891 save percentage and four Stanley Cup Playoff appearances.