The 38-year-old singer and designer had nothing but good things to say about Kardashian and her family during Tuesday's episode of Watch What Happens Live.
Hilton, who used Kardashian as a personal stylist in the star's early career, responded to those who credit her for Kardashian's success.
"I'm so proud of her. I think she's always been such an amazing businesswoman. She's so smart. She's gorgeous," Hilton said of her friend.
Hilton elaborated on Kardashian's previous hustles, which included closet organization services.
"She would organize people's closets and do that. Made a big business out of it, and then parlayed it into her brand now. Now she's selling makeup and clothing and everything else. She's killing it.
"I've known them since they were little girls," she said of Kylie and Kendall. "We all grew up together, and it's amazing what the entire family has done. They're all brilliant, beautiful businesswomen."
Hilton also dismissed rumors she feuded with Kardashian in 2011 after supposedly dissing the star's derrière on a radio show.
"I think it was the media just making something up," the star said. "But I just did a video called "My Best Friend's [Expletive]" and it has the most infamous [expletive] in the video. And her [expletive] is hot. I love it."
"We've known each other since we were literally two years old," she added of their lasting friendship.
Hilton and Kardashian teased Hilton's new music video in Instagram posts this month. TMZ said the pair were spotted on set in Los Angeles with RuPaul's Drag Race alum and Britney Spears impersonator Derrick Barry.