The 30-year-old beauty - who has been dating the basketball star for six months -went into "shock" when she walked into her Beverly Hills home to see him on one knee holding a 20.5 carat Lorraine Schwartz diamond ring.
She said: "I didn`t expect this at all. I was in such shock. I never thought it would happen at home, and I never thought now."
Kris had Kim`s mother Kris Jenner on hand to help him pick the ring, and the pair celebrated with all of her family after she said yes.
She added to People magazine: "Kris really didn`t want a big celebration, but he had jokingly told my mom he`d be fine if there were mini-horses there.
"Later that night at the party, my mom brought out two mini-horses, covered in glitter, for us. It was hysterical!"
Socialite Kim has previously said she has not been able to find any fault with him since they began dating.
She revealed: "I think I haven`t found one thing wrong with him, let`s just put it like that."