After pictures of Disick and another women in Monte Carlo surfaced, E! News exclusively reported the couple had called it quits.
The couple, dating since 2006, have three kids together: Mason, 5, Penelope, who turns 3 on Wednesday, and 6-month-old Reign.
"Kourtney has always taken Scott back and been by his side, but now with three kids it has gotten old," a source said. "Kourtney has to do what's best for the kids."
During the various seasons of Keeping Up With the Kardashians and its spin-off series, Disick battled substance abuse problems which affected their relationship.
Disick checked himself into rehab earlier this year and Kardashian told E!, "He's doing well, and you know, focusing on himself and working on himself. He's made a lot of progress, so I'm proud of him."
But now his partying antics have cost him his relationship with the 36-year-old. "Scott has been running around saying he's single," The source said. "Kourtney dumped him after she saw the pics and he hasn't been home after a month-long party binge."
Neither Kardashian nor Disick have commented on the break up.