The original American Idol winner shed some tears on stage – and forced some from the Idol judges and the audience – as she performed on the show where it all began.
As Clarkson, 33, choked up – along with judges Jennifer Lopez and Keith Urban – show host Ryan Seacrest took to the stage, acknowledging the amount of emotion in the "incredible" song and performance.
"I'm pregnant and it's nostalgic and I can't believe it's the last season," the expectant mother said. "Yeah, really sorry I just bawled."
"I am still overwhelmed and in shock from last night. The response to 'Piece By Piece' has me in tears," Clarkson said in a statement Friday. "To say last night was nostalgic would be an understatement. It was an unforgettable moment and to have my family and friends there with me made it even more magical."
This isn't the first time Clarkson got emotional performing "Piece by Piece." In August, when she announced that she was expecting her second child – a son – the singer broke down as she made her way through the tune, inspired by her husband's great parenting.
It was announced last May that this season, the show's fifteenth, would be its last. Entertainment Weekly reported in January that Clarkson would return to the idol stage as a performer and guest judge.
It's unclear if this will be Clarkson's only appearance on the final season, but she certainly gave a noteworthy farewell.