Fox and Kardashian – who appeared together on stage at the MTV Video Music Awards earlier this month – stripped off to matching black cotton underwear while covering their chests with their arms.
One of the pictures showed the pair face-to-face with an apple between their lips.
Another showed Kardashian feeding Fox cherries.
“And those who were seen dancing were thought to be insane by those who could not hear the music,” Kardashian captioned her favourite snaps on Instagram.
She added: “I had so much fun shooting with Megan for the campaign. SKIMS really is my favourite for my undies, bras and basics – I think I would say that even if Kim weren’t my sister!”
Fox wrote on social media: “Kourt, forever isn’t long enough.”
Fox and Kardashian’s partners – musicians Machine Gun Kelly and Travis Barker – are also close friends.
Megan Fox and Kourtney Kardashian star together in steamy Skims advert
