Kris admitted it has been a "hard" decision to make, but she felt it was the "right time" to end the show.
Speaking to creator and executive producer Ryan Seacrest on his radio show, she said: "I think the number 20, well it used to sound good until 2020, but the number 20, it just seemed like the right time.
"I think for us to take a minute and breathe and everybody slow down a bit. Not slow down professionally, but just you know figure out what our next steps are.
"We've had such an amazing run and so grateful for every single moment and everyone we work with."
But the 64-year-old momager admitted she and her family are still processing the change.
Asked if it has sunk in yet, she admitted it "really hasn't".
She added: "It's funny, when we talked yesterday, I kinda had my wits about me and I thought I was really strong. And, you know, this is the right decision.
"Today I wake up and I was thinking about the first time you and I ever did an interview on the air, and I was so excited and so nervous.
"I woke up and was in the gym at 5 o'clock with Khloé and Kim and we just kind of sat there and looked at each other and said, 'Whoa, what a ride.' It was quite the morning."
