The SKIMS founder was in attendance for the first weekend of the "All I Want for Christmas is You" singer's Christmas-themed tour, "Merry Christmas One and All!" in California.
Over the weekend, Kim took to Instagram and shared a slew of videos to her Instagram Stories from Mariah's concert, which saw the famed Hollywood Bowl be turned into a total winter wonderland.
She first shared a video of Mariah donning a red sequin mini dress while getting her make-up and signature blonde waves fixed up by her entourage, and wrote over it: "Legendary!!!"
However, while Kim looked excited as can be about the concert, as did her daughter North and a friend of hers who tagged along, Chicago on the other hand appeared to already be "Christmas-ed out," and in a subsequent Instagram Story, she's seen seemingly fast asleep, covering her eyes with dark black sunglasses while resting on her mom.
"LOL," Kim wrote over the priceless video, and continued to enjoy the concert regardless, sharing more special clips from her night out.
In another video, she cheered on Mariah's 12-year-old daughter Monroe – who is twins with son Moroccan – as she rocked out on stage with a red electric guitar, sporting a red tulle skirt with a leather jacket and her signature brunette curls. "Go Monroe!!!" Kim wrote.
Monroe later joined her mom on stage once more, this time looking like a true princess clad in a shiny white dress and even a tiara, twinning with Mariah who was in a sequin gold gown, as the two performed a duet of Mariah's 1994 song "Jesus Born on This Day."
Mariah's Christmas tour kicked off on Wednesday, November 15, and she will be making close to 20 stops across the US and Canada, before concluding with a final concert on December 17 at Madison Square Garden in New York City.
She previously shared that both her kids – who she welcomed with ex-husband Nick Cannon in 2011 – would be joining her on the road, and during a recent appearance on Good Morning America, she joked: "I think my daughter is rehearsing more than me. I think she has it together more than me," even revealing that Monroe does have her mom's signature high-pitch, she just "has to play with it."
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