San Diego Fire responded to the blaze on the 2800 block of Broadway near 28th Street just after 1 a.m.
A detached building behind the house caught fire before quickly spreading to the rest of the house. Crews didn't know if anyone was in the home when they first arrived at the fire, and thus initiated a search and rescue procedure, according to Battalion Chief David Picone.
Though no one was living in the house, it was still packed with furniture, fire crews said. Because the building was older, firefighters had to contend with a greater number of power lines than in many newer structures.
The fire could be seen for several blocks, and roads were closed as crews battled the blaze. Around 20 firefighters helped knock down the fire.
No one was hurt. Investigators are still looking into what started the fire.