Swift was playing "Burning Questions" with host Ellen DeGeneres when DeGeneres asked her to name the most rebellious thing she did as a teen.
"Probably when I put Joe Jonas on blast on your show. That was too much. Yeah, that was too much.
"I was 18. Yeah. We laugh about it now, but that was mouthy, just teenage stuff there."
Swift confirmed her split from Jonas on The Ellen DeGeneres Show in November 2008 after a few months of dating. She also said she wrote the song "Forever and Always" about the singer.
"There's one [song] that's about [Jonas], but that guy's not in my life anymore, unfortunately," Swift said.
"Someday I'm going to find somebody really, really great who's right for me," she added. "He'll be wonderful, and when I look at the person, I'm not even going to be able to remember the boy who broke up with me over the phone in 25 seconds when I was 18."