The other is still at large and may be hiding in Bucks County, authorities say.
Tyler Lutz, 18, from Reading, and 16-year-old Dustin Lomas from Bristol Township escaped from Abraxas Academy in New Morgan Borough on Saturday night.
Police say Lutz was taken into custody after being spotted by a Tullytown Borough police officer.
Lutz was at a local carnival and was trying to blend in with carnival employees, state police said.
He was taken into custody without incident.
Authorities now believe Lomas may also be in the Bucks County area.
Anyone with information on his whereabouts is asked to contact the police.
Last September, nine teenagers broke out of the juvenile detention center but were all taken back into custody during a 10-hour search.