San Diego police did not disclose what the victim and suspect were fighting about, but said it happened about 2:45 a.m. alongside Newport Avenue near Abbott Street.
At some point during the altercation, the suspect stabbed the victim in his left side with a sharp object, according to San Diego police Officer Robert Heims.
The wounded man was taken to a hospital to be treated for non-life- threatening injuries, Heims said.
Police described the suspect as black with a light complexion, about 5 feet 5 and wearing a black bomber jacket and a white T-shirt.
He was last seen running north on Abbott Street, police said.