The firefighter is being taken to the hospital with non-life-threatening injuries as crews continue to fight the fire, which was classified as a four-alarm just before 1 a.m.
The blaze was reported at a two-story house at Market and Hattie streets. It was classified as a one-alarm working fire at 12:20 a.m. and upgraded to a second alarm five minutes later.
Just before 12:40 a.m., the blaze went to a third alarm.
Videos posted to the SF Firefighters 798 Twitter account show thick smoke and flames burning through the roof.
No further information was immediately available.
Stay with ABC7 News for the latest details on this developing story.