Lehner, who was set to become an unrestricted free agent, led the Golden Knights to the Western Conference Final with a .917 save percentage and four shutouts in 16 playoff starts inside the Edmonton bubble this summer.
The Golden Knights acquired the 29-year-old from the Chicago Blackhawks at last season's trade deadline. This extension will give Lehner some stability after playing for four teams over the past three seasons.
The extension will also only put further pressure on team management to make a decision about Marc-Andre Fleury's future in Vegas. After Fleury was replaced by Lehner in net for the playoffs, his agent tweeted a drawing of him being stabbed in the back by a sword with new Golden Knights coach Peter DeBoer's name on it.
Fleury, who turns 36 in November and has two more years left on a contract that carries a $7-million cap hit, says he'd like to remain a Golden Knight but his agent's actions and Lehner's new extension mean his name will be in the rumour mill all off-season.
According to CapFriendly.com, Lehner's extension puts the Golden Knights approximately $59,000 over the salary cap, meaning more moves will need to be made before the off-season is over.