"I have a feeling it will happen."
ET caught up with the 58-year-old America's Got Talent judge, and he spilled about the possibility of the boy band getting back together. One Direction split in 2016 after being discovered on British X Factor in 2010, where Cowell was a judge.
"I just think the legacy is too big not to go back to at one point. Plus they have enough songs. I didn't realize how many hits they've had... When they do get back together it will be a huge event," he told ET's Denny Directo at AGT's season 13 live show on Tuesday in Hollywood, California. "But look, they're all doing their own thing and they're all being successful. But I have a feeling it will happen. I really do. I'd love it to happen."
Cowell, who also revealed that he's currently working on a show in the U.K. with Louis Tomlinson, shared that what made One Direction so great was how wonderful each member -- Tomlinson, Harry Styles, Niall Horan, Liam Payne, Zayn Malik -- is on their own.
"Individually they were all great," he gushed. "The group was the launchpad, but, of course, everyone would love to see them back together -- even if it was just a series of concerts."
Now judging on AGT -- which airs Tuesday nights on NBC -- Cowell, who also previously served as a judge on American Idol, has seen many a memorable performance
"I've done these shows a long time and there have been moments -- whether its Kelly [Clarkson], Leona [Lewis], Carrie Underwood... Grace [VanderWaal], Camila [Cabello]. You always remember that one performance where you go, 'That's gonna make a difference.'"
Cowell witnessed one of those moments on Tuesday night, when 14-year-old Courtney Hadwin wowed with a performance of "Papa's Got a Brand New Bag" in the show's first live round of the season.
"That was one of those moments," Cowell said. "It was incredible."
Here's more on Hadwin's unbelievable performance: