The pair had already tweeted the news several weeks ago but the announcement was made officially today by ITV.
Flack will hold the fort during the audition tour while Murs is away on tour with One Direction before he returns in time for the live shows.
“I had a fantastic time on The Xtra Factor last year with my TV husband Olly, so, I can’t wait to get started on the show again,” Flack said.
“Even though Olly and I won’t be reunited in person until the live shows we will be together all the way in spirit, he’s bound to be calling me mid-interview to check what has been happening on the Judges tour to ensure he doesn’t miss out on any crucial gossip!”
Murs said: “I can’t wait to get back to The Xtra Factor this year, especially now my partner in crime Caroline is confirmed to be joining me. I know it’s going to be a great year and we’ll be grilling the judges and contestants more than ever before.”