Firefighters were called to the complex around 2:30 p.m. near Inyo and Van Ness.
Investigators say the woman was putting away Christmas decorations when she set a box on top of the stove that caught fire.
Sprinklers were set off in the apartment and contained the blaze to the single unit.
"The holidays...carelessness," said Thomas Cope.
The building was evacuated as a precaution, but no one was hurt in the fire.
Damage is estimated around $10,000.