The two boys, ages 14 and 15, who are both on juvenile probation, escaped from the Canyon Oaks Youth Center at 400 Edmonds Road at about 12:30 a.m., according to sheriff's Sgt. Bryan Raffaelli.
Sheriff's deputies conducted a yard-to-yard search with canine units and located the 15-year-old boy at Cordilleras and Bennett roads about 20 minutes after the escape, Raffaelli said.
Authorities are continuing to investigate the whereabouts of the second boy. He is described as white, 5 feet 5 inches tall and weighing 160 pounds. He was last seen wearing a gray sweatshirt and gray pants.
The Canyon Oaks Youth Center is operated by the San Mateo County Health Department's Behavioral Health and Recovery Services.
Health department spokeswoman Beverly Thames said the facility is an unlocked group home that accepts referrals from juvenile probation as well as the county's human services agency and the school system.