The teens were reported missing at about 6:10 p.m. from the Log Cabin Ranch School, a San Francisco Juvenile Probation Department detention facility at 500 Log Cabin Ranch Road in La Honda, San Mateo County sheriff's Lt. Ray Lunny said.
They were last seen by staff getting into a blue or aqua-colored car similar to a Toyota Corolla just down the hill from the facility, according to Lunny.
Lunny described the area as remote and said it would be difficult to run away on foot.
One escapee is 17, about 5 feet 11 inches tall and 160 pounds with black hair and brown eyes. He was last seen wearing a blue sweatshirt, blue jeans and black shoes.
The other is 16, about 5 feet 6 inches tall and 110 pounds. He also has black hair and brown eyes and was last seen wearing a white T-shirt, khaki pants and white tennis shoes.
Anyone with information is asked to call sheriff's Detective Marcus Gathright at (650) 363-7823 or the San Francisco Juvenile Probation Department at (415) 758-7800.