WWE.com says Lawler collapsed at the announcers' table and was tended to in the locker-room area by WWE medical staff.
The website says Lawler was taken from the arena to hospital.
Broadcast partner Michael Cole addressed the event's television audience and said that the situation was "serious" but that Lawler was breathing on his own.
"We are hopeful Jerry makes a full recovery and returns to WWE in the near future," the WWE said in a statement. "Our thoughts are with Jerry and his family."
The 62-year-old Lawler, who mainly works on WWE broadcasts as a commentator, was involved in a match earlier on Monday night's card.
"I'm shaken by the news of my friend Jerry Lawler's medical emergency in Montreal," tweeted longtime broadcast partner Jim Ross. "Hands shaking. Prayers for the King. I feel helpless."
Tweeted former WWE wrestler Shawn Michaels: "I've just heard about Jerry Lawler!! Time for prayer everybody!! We're here for you King, God Bless!!"