The attack happened while the couple was arguing in the area of Abbott Street and Newport Avenue shortly before 6:30 p.m. Thursday, according to San Diego police Officer David Stafford.
The man sustained a cut behind one of his ears and was taken by ambulance to an area hospital for treatment, Stafford said in a statement. He was expected to survive.
The woman was arrested near the scene on suspicion of assault with a deadly weapon, he said. Her name was not immediately released.