The blaze in the 4100 block of Gamma Street erupted for unknown reasons shortly before 4 p.m., according to the San Diego Fire-Rescue Department.
It took crews about 20 minutes to extinguish the flames, SDFRD Capt. Joe Amador said.
The American Red Cross was called in to held the displaced residents -- six adults and three children -- arrange for interim shelter.
The cause of the fire, which apparently erupted on an exterior wall of the residence, was under investigation, the captain said.