The former Pussycat Doll opted for a tuxedo dress and sky-high heels for filming on Monday, 13 June alongside fellow judges Simon Cowell, Louis Walsh and Sharon Osbourne.
Nicole's returning to the show this year after judging during series 9 and 10, while Louis returns after a one-year hiatus and original judge Sharon is also back on the panel.
"I can't wait to be back in the UK and on the show with the best judges sitting alongside me on the panel," she said. "I'm excited about discovering, mentoring and winning with an exciting new act this year. And having had winning contestants in the past, Simon knows I will do it."
Nicole previously guest judged alongside Sharon and Louis (and Gary Barlow) in 2013, while she worked with Simon on X Factor USA.
"I'm so excited! I miss England. I haven't been there in a while. It's my second home and I'm happy to be reunited with Shaorn and Louis. I haven't seen them in a while. And Simon, of course!"
As well as a new-look judging panel, there is a new host! Well, new returning host… Dermot O'Leary is back presenting the series, after last year's hosts Caroline Flack and Olly Murs left.
X Factor is bringing back the intimate room auditions for series 13, which means hopefuls must wow the majority of judges in a private audition room, before hitting the arena stage to sing for thousands.
The show returns to ITV later this year.