No homes are threatened by the blaze, which was reported at 11:09 a.m. near South Hill Drive, fire spokesman Matt Lucett said.
The fire worked its way up a hillside, prompting a two-alarm response that has included a helicopter and two Cal Fire hand crews -- one of which was nearby when the fire started, he said.
"We were fortunate to have a Cal Fire hand crew in the city of Brisbane at the time working on some vegetation management," Lucett said.
As of 1 p.m., the fire was 25 percent contained. Lucett estimated it would take several more hours to put the fire out.
No injuries have been reported and no structures damaged.