Rick Scriven, safety officer with Eastside Fire & Rescue, said the off-duty firefighter was driving by the home, in the 13600 block of 432nd SE, when he noticed smoke and flames at about 9:15 p.m. Friday.
The firefighter stopped, and a neighbor told him that the woman was still inside the home, so he ran inside and rescued her.
"He was able to go and grab the occupant, drag the occupant out of the structure and into the front yard," Scriven said.
Someone called 911 and fire crews arrived within moments - but by then flames had engulfed much of the home.
Scriven said it was a difficult fire to fight and the home was a total loss.
The disabled woman and another occupant of the home were taken to a local hospital to be treated for minor injuries and smoke inhalation.
The cause remains under investigation, but the preliminary conclusion is that the blaze was started by candles, Scriven said.