ET caught up with Kris on Saturday at Williams-Sonoma at The Commons in Calabasas, California -- where she was promoting her cookbook, In The Kitchen with Kris: a Collection of Kardashian-Jenner Family Favorites -- and shared that the sexy picture actually caught her off guard.
"Well, when you think no one's looking, you do some things that you know -- I wouldn't necessarily walk around like that except if I was on my own, or on my own vacation," Kris told ET's Kevin Frazier.
She absolutely denied any speculation that she's had a tummy tuck.
"What I thought was funny was I saw someone posted that picture, and people's comments were like, 'tummy tuck!'" she laughed. "And I'm like, 'tummy tuck?' I had no tummy tuck."
But even though she looks great, Kris did admit to having some bikini insecurities at her age.
"After six kids you're not as confident -- and 59 years old! -- [as] you might be if you were 25 years old with no kids," she explained. "So it's kinda scary to put on a bathing suit and just hang with the kids sometimes in public."