The teen pop sensation posted a photo Sunday of himself with the reality-TV star – with her holding a flower – taken on the beach during a photo shoot at the Atlantis Resort in The Bahamas.
"Photoshoot on the beach ... ummmm yeah. I told her to watch out ... I love my fans," Bieber, 16, wrote on Twitter.
Kardashian, 29, then posted her own photo showing her running her hands through Bieber's famous locks. "My dream! I messed up Justin Bieber's hair!!!" she Tweeted.
Some Bieber fans will surely get riled up by the images, having already strongly objected to Bieber's friendship with Kardashian after they met at the White House Correspondents' dinner in May.
Kardashian, who admitted to having "Bieber Fever" at the time, said she even received death threats. Bieber tried to calm things down, calling Kardashian "a very sexy friend but a friend. No need 4 threats. Let's all be friends and hang out often."