Four other youths were involved in the attack, reported about 4:30 p.m. on a bus near Stockton and Sutter streets. Police have arrested one suspect, Officer Robert Rueca said.
RELATED: Person stabbed on Muni bus in San Francisco, police say
The victim's condition was initially listed as life-threatening, but Rueca said Tuesday that the teen was recovering.
Police aren't releasing what led to the stabbing or any other information about incident, other than the investigation is "active and ongoing," Rueca said.