The blaze was reported around 4 p.m. in a remote area along Castaic Lake Drive, but it quickly grew in size. A few hours after it ignited, firefighters managed to stop forward spread of the flames.
The fire was 50% contained as of Sunday morning after charring an additional 8 acres overnight.
The fire burned in the Angeles National Forest but Los Angeles County firefighters were assisting in the fight.
Crews were expected to stay on scene overnight to build containment lines and stamp out any hot spots.