"When I hit him with the right hand the first time, his body language changed," Wilder said.
And with the last one, Breazeale's body language crumpled.
Wilder (41-0-1, 40 KOs) was coming off his draw against Fury in December, the first fight of his pro career that wasn't a victory.
He wanted a rematch with Fury or a unification match with fellow champion Joshua but settled for a mandatory defence of his WBC title when those couldn't be made.
He ended it quickly, finishing off Breazeale (20-2) after being pushed hard in each of his last two fights.
Wilder weighed in at a little more than 101kg, a gain from the 94kg he was at for the Fury fight, but still well below the 110kg he set as a goal after feeling he was too small in that bout, in which he dropped Fury with a huge combination in the 12th but had to settle for the draw when the challenger got up and finished the fight.
An immediate rematch was expected before Fury surprisingly went another route.
"I understand what Tyson Fury did. When you get dropped on the canvas like that, I understand you have to get yourself back together," Wilder said. "But the rematch will happen, like all these other fights will happen. The great thing is all these fights are in discussion. The big fights will happen."
And Wilder won't need any more weight as long as he still has one of the most feared right hands in boxing. Breazeale had downplayed Wilder's power but he should certainly be a believer now.
- AP