The 32-year-old reality TV personality and father of three young children went away with his guy friends, but has been spotted all week flirting and cuddling with various women, including celebrity stylist Chloe Bartoli, E! News reported.
His behavior has his concerned friends calling his Los Angeles home to update Kardashian.
"They fear he is out of control and has fallen off the wagon," a source close to Disick said.
"He is partying hard and they are concerned," the insider added, noting Kardashian and Bartoli "are not friends."
Kardashian hasn't publicly commented on Disick's alleged exploits, seemingly preferring instead to take the high road and post on Instagram a cute photo of herself and their children enjoying a pajama party while he is away.