The 18-year-old victim was walking near Cortland Avenue and Elsie Street around 6 a.m. Tuesday when a man approached him and demanded his money, according to police.
When the victim refused, the suspect stabbed him with a knife and then fled on foot, police said.
The victim is expected to survive his injuries.
The suspect, described as a man about 20 years old, has not been found. Anyone with information about the stabbing is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.