The Chicago Bulls player, 31, posted a snap captured at the cat-themed soiree on Sunday, giving a glimpse at the pastel balloon arches and pool inflatables set up in the backyard while he was away at a game.
"Tutu's uncles don't play," he captioned a photo from the event.
True's fun-filled shindig, joined by her cousins, came days after her famous family members gathered for the L.A. premiere of their new Hulu show, The Kardashians.
According to a report, Khloé Kardashian yelled at the screen from her seat when her ex Tristan made an appearance on the show.
During one scene in particular, the NBA star talked about "working on regaining her trust" after his past cheating scandals.
An onlooker said that "someone in the audience screamed, 'Liar!,'" and moments later, they realized "it was Khloé. She yelled super loud, 'Liar.'"
"She jokingly said, 'Liar,'" the onlooker clarified. "People were laughing. She was in an amazing mood and spirits."
Earlier this year, Tristan spoke out after paternity results confirmed he fathered a child with Maralee Nichols, the fitness trainer who claimed she and the power forward conceived in March 2021 — at which time he was still in a relationship with Khloé, 37.
"I take full responsibility for my actions," Tristan, who also shares son Prince with ex Jordan Craig in addition to True with Khloé, wrote in January. "Now that paternity has been established I look forward to amicably raising our son. I sincerely apologize to everyone I've hurt or disappointed throughout this ordeal both publicly and privately."
He also directly addressed the Good American founder and apologized for his actions. "You don't deserve the heartache and humiliation I have caused you," Tristan continued his statement. "You don't deserve the way I have treated you over the years. My actions certainly have not lined up with the way I view you. I have the utmost respect and love for you. Regardless of what you may think. Again, I am so incredibly sorry."
Since then, Khloé has embraced her single status and hinted that she doesn't want to get back with her off-again ex after their latest split last June.
While appearing on The Kardashians: An ABC News Special, Khloé said that Tristan is still "a great guy" and a great father to True, but he is "just not the guy for me."