The juveniles were reported missing just after 9 p.m. from Camp Glenwood, located at 400 Log Cabin Road, San Mateo County sheriff's Lt. Ray Lunny said.
Camp Glenwood is a facility for delinquent teenage boys. The four inmates who walked away Sunday had committed non-violent crimes, Lunny said.
The teens are believed to have fled the facility as they were returning to their dorm rooms after their evening recreation period, Lunny said.
Three of the boys are 15 years old and the fourth is 17. Two of the 15-year-olds are Hispanic and one is black, and all three are between 5 feet 5 inches and 5 feet 10 inches tall. The 17-year-old is Hispanic and 5 feet 1 inch tall.
All four were wearing blue jeans and gray sweatshirts.
Anyone with information is asked to call Detective Marcus Gathright at (650) 363-7823.