It happened late Thursday afternoon at Delphine Gallery on the 8400 block of Germantown Avenue.
Police say an armed man came into the shop wearing a long, dark navy blue dress, a dark braided hair wig and a white silk mask.
The suspect allegedly told a female employee to get down on the floor, while he took $50,000 worth of jewels from their cases.
The suspect later fled the scene in a light green Ford Explorer which was being driven by another male.
No one was injured during the robbery.
Anyone with information is urged to contact Philadelphia Police.
