It happened just before 2:00 a.m. Tuesday at the Sunoco located on the 300 block of E. Street Road in Feasterville, Bucks County.
The suspect threatened the clerk with the tire iron then made off with the register heading east on Street Road.
There were no injuries reported.
Employees told police the man wore a pillow case over his head with holes cut out over the eyes and mouth. He is described as a white male, 6'2" wearing a brown jacket.