The couple was spotted enjoying a date night at both the Greenwich Hotel and Bowery Hotel in New York City on Saturday.
"They were very cuddly and cute," a source tells E! News. "Katy definitely gave the impression that she and John are 100 percent back together."
What's more, an eyewitness says Perry made it a point to show everyone around her that she and Mayer were an item again.
Earlier this month, we broke the news that the couple was "back on," although sources told us at the time that "they are just hanging out" and "not putting a label on it."
Perry, meanwhile, reveals in the latest issue of Vogue that she is still "madly in love" with Mayer.
—Reporting by Baker Machado