The pair will present the ITV2 spinoff for a second year, though Flack will cover the auditions, Boot Camp and Judges' Houses alone while the 'Dance With Me Tonight' is on tour with One Direction in the US.
Murs will be "recording special items" for the series in his absence, before rejoining his colleague at the live shows.
Flack said: "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.
"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 added: "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."
Flack had personally confirmed her return to The Xtra Factor back in March, while Murs said on Daybreak this morning that he had "officially signed on the dotted line".
The pair were frequently romantically linked throughout last year's series, but always denied the rumours.
Elsewhere on The X Factor, Louis Walsh and Gary Barlow have been confirmed for the judging panel, with Tulisa Contostavlos expected to return.
Dermot O'Leary will host the ITV series for a sixth year, while guest judges will fill in for departed panelist Kelly Rowland.
Geri Halliwell is tipped to both guest at auditions in Liverpool tomorrow (May 23) and take a permanent judging role later in the contest.
