Unbeaten heavyweight champion Joshua, 26, floored Breazeale twice in the seventh round before the referee waved off the bout as the British star improved to 17-0 with a 17th knockout in London on Saturday.
In his first title defence since dethroning Charles Martin in April, Joshua flexed his muscles at O2 Arena, though Breazeale proved a resilient opponent.
After dictating the sixth round, Joshua stormed out of the blocks in the seventh, with a stunning combination sending Breazeale to the canvas.
However, Breazeale somehow got to his feet only to come crashing back down again for good as the Joshua juggernaut rolled on.
"It was a matter of timing and a process. I didn't want to take any haymakers on the way back," Joshua said post-fight.
"I only had two weeks off after my last fight and now I want to have a nice bit of time off. I was looking at Tyson Fury and I hope he gets better soon because I was hoping to get that in the winter. In the meantime, we'll look at other opponents like Joseph Parker.
"I need to rest. I'm tired and I'm working hard. Now I can recharge my batteries and start afresh again."