Charlotte was speaking to Newsround Showbiz about her first movie, I'll Be There, when she dropped it into the conversation.
Charlotte says: "My agents approached Warner Bros about me being Hermione.
"Eventually they decided I was too old," she explained."I was 13 at the time, and they needed someone about 11, it was so sad".
Potter potty
Charlotte also talked about the much-awaited fifth Potter book: "I am so excited, I've got my order in. I can't wait!
"I read all the books so many times!"
You can watch Charlotte's full interview with Newsround Showbiz on the CBBC channel on Friday at 6:50 pm.
Hear story 
Chat about non-pop music
Try our Charlotte Church quiz
