The singer had to take on a last-minute challenge due to the birth of James Corden's third child.
He stepped in to host The Late Late Show in the US as James and his wife Julia welcomed a baby girl.
James announced the birth on Twitter, saying both mother and baby are doing well and they couldn't stop smiling.
He also thanked Harry for hosting the show after getting just two and a half hours notice.
Here's how Harry handled the hosting gig.
