The 68-year-old shared a photo with Hutchins and Kylie from the celebration on Instagram Friday.
“Had so much fun in the photo booth at @kyliejenner’s birthday party!” the former Olympian captioned the post, which shows Kylie doing her signature pout as Caitlyn and Hutchins smiled.
Both Caitlyn and Hutchins dressed up for Kylie’s big night. Caitlyn opted for a colorful sequin dress paired with a black Gucci bag, almost identical to the one ex-wife Kris Jenner wore for the evening.
Meanwhile, Hutchins wore a gold mini dress with her hair styled in loose waves.
However, Kylie stole the show in a pink sequin LaBourjoisie unitard.
Over the past year, there has been speculation over whether or not Hutchins and Caitlyn are dating.
Caitlyn recently addressed their relationship during an interview.
“We are not going to get into that,” Caitlyn told Variety. “But we are very close.”
“We do a lot of things together. We’re kind of inseparable,” Caitlyn told the publication. “We’re the best of friends.”
The duo also attended the 2018 ESPY Awards together in July.
“Sophia and I off to the ESPY’s. Bringing back old memories of my first public outing. Life is good!” Caitlyn said in reference to her 2015 ESPY Awards appearance, which was her first major appearance since transitioning.