The fire damaged two three-story Victorian houses at 1214 and 1216 Fulton St., according to the San Francisco Fire Department.
There were no reported injuries in the blaze.
Five people were displaced, including an infant, according to the fire department.
The fire has been reported as under control, but residents are asked to avoid the area due to an active scene.
The fire was first reported around 3:30 a.m.