The couple dated for several weeks before deciding their relationship "was moving too fast," the unnamed insider said.
They are "better off as friends," the source told UsMagazine.com.
Aubry has a 2-year-old daughter with actress Halle Berry, who he broke up with last April after five years together.
Kardashian dated professional football player Miles Austin for a few months before splitting from him in September.
Swim Week Miami Beach 2014 [PHOTOS]