The girls had left their sister waiting for her personal trainer for half an hour – after they turned up late to their session with the same coach.
And Kim took to Snapchat to let them know just what she thought of them.
“So me and my friend Nikki are waiting for [our trainer] Joe to get here because my sisters’ workout ran 30 minutes late,” she said.
She added: “Okay. Seriously, Kourtney and Khloe: f**k you. This is so rude. I have been sitting in my garage waiting for the trainer for 30 minutes. I do have a life.”
When coach Joe finally arrived, Kim took to Snapchat to say: “Oh look who decided to show up! Look who decided to show up. Who was late? … Tell me, Joe. Who was late?”
Joe admitted that Kourtney, 37, was to blame for the delay.
“Oh, Kourtney. Okay,” said Kim.
Khloe hit back on her own Snapchat, calling Kim “The queen of being late for workouts.”
Kourtney justified her lateness to Khloe saying: “You’ve been hanging out with me in the kitchen!”