Police were called to Cobra nightclub near King Street West and Spadina Avenue at around 12:30 a.m. Saturday.
Police at 14 Division said the man was stabbed in the chest but it wasn't immediately clear if the incident happened inside or outside the club.
There were no arrests made and police are still investigating what may have led to the stabbing.
In August, two men were taken into custody after a shooting at the same nightclub.
People were filing out of the club when shots rang out injuring at least two people, including a bouncer.