Police spokesman Officer Albie Esparza said the fight took place at about 1 a.m. outside Club Malibu at 3395 Mission St.
During the fight, the suspect, a man in his early- to mid-20s, took out a knife and stabbed the 34-year-old victim once in the back, Esparza said. The suspect then fled and has not been found.
The victim was taken to San Francisco General Hospital and is expected to survive, Esparza said.
Esparza said it was not immediately clear whether the fight had anything to do with activity at the club.