Disick, 31, was nowhere to be seen as his partner, Kourtney Kardashian hosted North's first birthday party at their home, reported Female First.
He was reportedly partying at a nightclub with a mystery female.
"The reality star arrived with his entourage of male friends at 12:30 am," a source said.
Disick apparently did not leave the venue until four in the morning.
The news of Disick missing North's birthday party comes days after he was reportedly thrown out of the Kardashian family's rented estate in the Hamptons on June 14 due to his wild partying ways.