The blaze was reported at about 5:30 a.m. at a two-story house in the 2900 block of Hastings Avenue.
When the smoke alarm went off, the woman got out of bed to investigate and found the fire burning in the garage area, Battalion Chief Dave Pucci said.
She grabbed her dog and her cellphone and called the fire department on her way out, he said.
Firefighters arrived and controlled the blaze. No injuries were reported, but the home sustained significant damage, Pucci said.
Pucci underscored the importance of smoke detectors.
"She's very lucky the alarm woke her up because it could have been very bad otherwise," he said.