"On November 7, 1988, Leonard made another comeback, facing Don Lalonde at Caesar's Palace in Las Vegas. They fought for Lalonde's WBC Light Heavyweight Championship and the newly created WBC Super Middleweight Championship, which meant that Lalonde had to make 168 lbs. Many were critical of Leonard for stipulating that his opponent—a natural 175 pounder—should weigh less than his usual fighting weight, weakening him.

Lalonde, 31–2 with 26 knockouts, was guaranteed at least $5 million and Leonard was guaranteed over $10 million.

Lalonde's size and awkwardness troubled Leonard. In the fourth round, a right hand to the top of Leonard's head dropped him for just the second time in his career. Early in the ninth, Lalonde hurt Leonard with a right to the chin. Leonard fired back and hurt Lalonde with a right. He drove him to the ropes and unleashed a furious assault. Lalonde tried to tie up Leonard, but got dropped with a powerful left hook. He rose but was soon down again, and the fight was stopped. Judges Chuck Giampa and Franz Marti had Leonard ahead by scores of 77–74 and 77–75, respectively. Judge Stuart Kirshenbaum had Lalonde ahead 76–75."