"Yes, I wrote a song with Harry," she told host Nick Grimshaw, Styles's BFF. "It was unbelievable. He's a very, very talented songwriter – I was very impressed."
Trainor had also revealed her collaboration to the U.K.'s Sun earlier on Tuesday, telling the outlet more specifically that the pair had written a "cute acoustic love thing" on her ukelele.
Also read: Harry Styles' New Direction