"I couldn't be happier that Demi wants to come back this year," judge and producer Simon Cowell said in a statement to EW.com Thursday. "She's a superstar in her own right and was a fantastic mentor last year. Even though she can be really, really annoying -- I truly enjoyed working with her and so did the artists. I'm especially pleased she's back even during her world tour."
"I am so excited to return as a judge and mentor on 'The X Factor,'" said Lovato. "Last season was an unbelievable experience and I really enjoyed developing personal relationships with the contestants and the panel. I look forward to taking my previous experience and applying it to make this season even better."
Their replacements have not been announced yet.
2014: The Year in Music [PHOTOS]