The blaze erupted shortly before 9 a.m. at the former Hollywood Playhouse in the 1400 block of North Las Palmas Avenue, according to the Los Angeles Fire Department. A column of smoke that rose into the air above the scene was visible for miles.
No injuries were immediately reported.
Dramatic fire erupts at vacant theater in Hollywood
The intensity of the fire initially forced firefighters to pull back into "defensive mode, with a focus on protecting the surrounding buildings first," the LAFD said. Officials expressed concern that the walls of the burning structure, which was built about a century ago, might collapse.
Video from AIR7 HD showed firefighters on adjacent rooftops and aerial ladders dumping water on the flames that were shooting through the roof of the theater, which eventually caved in. By 10 a.m., the LAFD seemed close to fully extinguishing the fire. An official knockdown was declared just before 11 a.m.
Nearby Sunset Boulevard was closed between Highland Avenue and Cherokee avenues as the LAFD remained on scene. The street closures led to snarled traffic in the area.
The cause of the fire was under investigation.