It happened at 12:45 a.m. Sunday at Dan Doubet Jewelers in the Ridge Village Shopping Center in Concord Township.
Authorities say surveillance video shows a man wearing a ski mask and gloves kicking through the glass front door, entering the store and stealing items on display.
The thief made off with about $3,000 in jewelry.
Police are looking for a man about 6 feet tall last seen wearing blue jeans and a blue collared shirt with short sleeves.
Anyone with information is asked to call the Pennsylvania State Police Media Barracks at 484-840-1000.
