Taking to the photo-sharing site, the 41-year-old mum-of-three was keen to show the fun and frolics she was having with her bestie – 19-year-old TikTok star, Addison Rae.
The duo have been enjoying some time at Kourtney's pad along with her other close pal, Simon Huck.
Kourtney shared two snaps of she and Addison enjoying some downtime at her pool, and they couldn't resist in posing up a storm for the camera.
One picture saw Addison lay on a beach towel, as she shielded her eyes from the camera.
The TikTok star looked incredible as she rocked an aubergine-coloured string bikini, which showed off her gym-honed frame.
Kourtney's bikini complemented Addison's, as she rocked one in the same style, instead opting for one in a chic teal hue.
Kourtney accessorised with a wide-brim sunhat and a pair of sleek shades, while Addison opted to go accessory-free.
A later duo snaps posted by the Poosh owner, saw Addison and Kourtney pose in the swimming pool.
Rocking wet locks and au naturale makeup, one shot saw Addison tenderly rest her head on Kourtney's shoulder, while Kourt smiled at the camera.
The other, saw Addison and Kourtney both in a fit of giggles.
Fans flocked to shower praise on the besties' impromptu photoshoot.
One social networker remarked: "Such a beautiful pic."
While another continued: "Besties!"
A third added: "Wow!"
Addison Rae Easterling is an American social media personality and TikTok star, who has amassed over 56million followers on the video-sharing site.
It's unknown how she and Kourtney have become besties, but we wonder if she'll pop up in a KUWTK soon?!