It happened at the 901 Cottman Avenue location just before 2 a.m., authorities said.
The gunman walked up to an assistant manager outside, struck her in the face with a pistol, and forced her into the store, according to investigators.
Inside, he pistol-whipped the 25-year-old again and held all the employees at gunpoint but was not able to open the restaurant's safe, police said.
He ran east on Cottman Avenue and is still being sought by detectives. Police said he was wearing a black hoodie with a black ski mask and carrying a handgun.
Anyone with information can call PPD's tipline at 215-686-8477.
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