The 26-year-old socialite - who is married to basketball star Lamar Odom - admits she lied about her age when she met a mystery man who she used to see for secret dates.
The brunette beauty would even steal her stepfather Bruce Jenner`s car or her mother Kris Jenner`s vehicle to go and hook-up with the guy.
She recalls in a new book she penned with her sisters Kim and Kourtney, `Kardashian Konfidential`: "This guy was very, very manipulative, and I ended up losing my virginity to him when I was only 14. When my dad found out I was having sex, he went ballistic.
"My mom taught me how to drive when I was 13, so if one of our baby sisters had an emergency I could drive to the hospital. But I took advantage of it. I used to steal her car or Bruce`s, and I`d go over to this guy`s house. He was a lot older than me, though he lied and said he was younger. Of course, I lied, too, and said I was 16. I was doing really well in school until I met him."
Khloe eventually stopped the relationship and now realises it was a mistake to lose her virginity at such a young age.
She added: "I was only 14, but I thought I was so mature, and I look back and see how wrong I was. Having sex for the first time is an extremely important decision that affects your whole life.
"You should never, EVER have sex when you`re that young. Feeling rushed and pressured and unsure should have been my clue that I wasn`t ready to take that step."