Kanye joined in as they supported host Khloe.
She has been hosting the X Factor USA live shows for three weeks now.
But since she began her very first stint on the reality TV contest, surprisingly her famous family have been noticeably absent in the audience.
That is until now.
Nearly the entire Kardashian clan came out in full force on Wednesday night to watch the statuesque 28-year-old take the stage with co-host Mario Lopez.
Sisters Kim, Kendall and Kylie Jenner, mother Kris, step-father Bruce and even Kim's boyfriend Kanye appeared at the show to support Khloe. Kim was seen arriving at the Los Angeles studios in typical Kim fashion.
And once again the Keeping Up With The Kardashian star wore her favourite leather.
But after a succession of bad outfits, this time she got it right, her curves looking sensational in a scarlet red pencil skirt paired with a black low-cut and sheer blouse.
The raven-haired star accessorised the outfit with black stilettos and carried her favourite little Chanel clutch bag.
Kim was flanked by her boyfriend Kanye and younger sisters Kendall and Kylie Jenner as she entered the building.
Meanwhile, super tall Kendall opted for a pair of shorts with tights worn underneath and a black blouse.
She boosted her already statuesque height with copper heels and like her big sister wore her famous brunette locks out in a straight style.
Kylie also opted for leather in the form of trousers teamed with an oversized black T-shirt.
Meanwhile Kanye, who could barely raise a smile, was dressed in his obligatory head-to-toe black, albeit a pair of white high-top sneakers.
Before they headed into the studios, Kendall helped her sister Kim, who appeared to be suffering from a wardrobe malfunction.
The 17-year-old bent down to do up Kim's skirt which appeared to have come undone.
Throughout the evening the clan could not help but excitedly tweet their way through the show, posting endless updates and photographs.
Kim posted a snap of herself and her two younger sisters Kendall and Kylie sitting in the audience.
'XFactor were in the building!!!! @kyliejenner @kendalljenner,' she captioned the picture.
The reality TV star also posted a photo of her sister Khloe onstage, proudly writing: 'Khloe looks stunning tonight on X Factor! So proud of you @khloekardashian!!! You were born to do this!'
Just before she went onstage, Khloe posted her very first Keek video of herself backstage.
Dressed in a fitted white mini dress and her hair coiffed to perfection, she said in the short clip: 'Ooh this is my first keek or keegle as I like to call it. I am backstage at the X Factor and I am about to go on!'
The family's show of support comes as Khloe had a little bit of a scare earlier this week.
A letter containing a suspicious white powder and addressed to Khloe was intercepted at the CBS studios where The X Factor is filmed in Hollywood on Tuesday.
Sources told TMZ that the letter arrived to the studio in the morning 'and the FBI soon arrived to inspect the mystery substance.'
According to the entertainment website, the substance was found to be harmless.
A letter was also included; the contents of which have not been divulged.
Two letters were sent to Bristol Palin at the same studio, and just as in this case the white substance turned out to be harmless talcum powder.
The X Factor and Fox declined to comment.
But a source told E! News: 'Khloé is fine. 'The studio has hired extra security. Khloé is heading to rehearsals right now. She is not worried.'
She revealed that Lamar, 33, watches her stints in front of the camera via YouTube whenever the NBA star is on the road.
The youngest Kardashian told People magazine that he lovingly mocks her voice in the videos but that he also made a reference to Boob-gate.
'The only tip he gave me was don't show your nipples anymore,' Kardashian joked to the magazine.
'He said: "Please do not have your [breasts] out." I said, "Oh, good tip."'