'The Kardashians' star marked the milestone on Thursday and she gathered her family and friends together on Saturday for a lavish bash which was themed around country legend Dolly - featuring a "Khloewood" sign inspired by the singer's Dollywood theme park - above the DJ booth as well as "Khlo$ Saloon" bar and a a mechanical bull.
Khloe wore a denim corset and matching chaps while her guests - including sisters Kim and Kourtney - all got the memo and were seen wearing denim outfits. Others at the bash included family matriarch Kris Jenner, Khloe's half-sister Kylie Jenner and Kourtney's husband Travis Barker.
Before the bash, Khloe shared a video of herself getting ready on Instagram and wrote: "Oh My Dolly it's time to party!"
Drinks served during the party included the Espress-Khlo Martini and the No. 1 Most Wanted as well as Show me the Khlo-Money and Raspberry Rogue.
The party included performances by Snoop Dogg, Warren G and Kurupt.
The party comes after Khloe previously admitted she felt excited about turning 40 because she is "shedding" her old life and embracing a "new version" of herself.
Khloe had been counting down the days until she starts the new decade because she sees it as a representation of a new era following a turbulent few years which included the breakdown of her relationship with boyfriend Tristan Thompson, the father of her two children.
Khloe told Grazia magazine: "I'm going to be 40 in June and I think most people are nervous or get weird about it and I am counting down the moments until that day.
"I feel like I'm shedding so much of my old life, an old version of me, and I'm so excited for this new version,' she explains. 'I know it's so hugely clichéd to say it, but with age and experience comes wisdom, and that wisdom brings me more peace."
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Khloe Kardashian throws Dolly Parton-themed 40th birthday party
Khloe Kardashian celebrated turning 40 by throwing a Dolly Parton-themed birthday party for her friends and family complete with a "Khloewood" sign, a mechanical bull, denim outfits and cowboy hats as well as performances by Snoop Dogg, Warren G and Kurupt