The 32-year-old beauty - who has 17-month-old son Mason with her partner Scott Disick - explained while her rear is her best feature, she has to work out to ensure she doesn`t get unsightly "saddlebags".
She said: "I love my butt, but I have a tendency to get saddlebags there. So I need to watch it."
However, the trim star credits her active sex life for allowing her return to her pre-baby weight quickly, as she thinks bedroom action is "great exercise".
Kourtney added to Shape magazine: "Sex is great exercise!"
While Kourtney may be happy with her figure, her sister Khloe, 26, recently admitted she has been on the receiving end of cruel "fat" jibes.
She said: "I`m the ugly sister. I`m the fat one. I`m the transvestite. I have had those mean things said about me at least twice a day for the last five years. It`s horrible, you know? But I can brush that stuff off."