In a sneak peek clip of Monday night's episode, Swift, this season's Mega Mentor, breaks down in tears while watching rehearsals for Team Kelly Clarkson's duo, Hello Sunday. The duo, which is compromised of 14-year-old friends Chelsea and Myla, opt to sing Ariana Grande and Nathan Sykes' 2013 track, "Almost Is Never Enough."
"Oh my god, I'm fully crying," Swift tells Clarkson following the girls' performance. "I don't know why. It's just really, really great."
"When I started out, I was 10 or 11 years old singing for people," Swift adds in a confessional. "But seeing young performers, who so firmly have their musical identity figured out, I was completely shattered by it. I fully fell apart. It was that good."
Alex Guthrie, whom Hello Sunday will compete against in the knockout round, is certainly a little nervous after watching Swift's reaction to the teens.
"Hello Sunday brought Taylor Swift to tears. I definitely have my work cut out for me," he says. "They're really talented beyond their years."
While still wiping away tears, Swift, along with Clarkson, make their way up to the stage to further praise Hello Sunday on their triumphant performance.
"Oh my god, it was good. The amount that you were connecting with each other, the amount that you were then facing out and connecting with the audience," Swift tells the duo as she continues to cry. "Oh my god! I'm so sorry. I promise I'm OK in my personal life. This is not from some outside place... Literally at any age that would've moved me like that."
Hello Sunday, meanwhile, was thrilled by Swift's reaction to their song.
"When she walked on that stage with tears in her eyes... it assured us that we can actually move people when we sing," they say.
As for Clarkson, Swift tells the three hopefuls that their coach is "in a difficult situation."
"She finds herself in a complex predicament," Swift says.
Back in September, fellow Voice coach Blake Shelton told ET what made Swift such a great mentor this season, following her season-seven run in the role in 2014.
"She did great as a mentor and she did it the first time and then coming back in this second time, it's like she's made for that," he said. "She's super smart and she’s really good at looking at somebody's performance and listening to them and being able to go, 'I know a couple things here that instantly, I think, we can tweak on and it will take it to the next level.' She's really good at that."
The Voice airs Mondays and Tuesdays at 8 p.m. on NBC.