It happened in the 200 block of Lancaster Avenue in the Wayne section of Radnor Township at 3:56 a.m.
A man wearing a white hoodie and a mask made from a torn t-shirt entered the store and started banging on the counter.
Police say the man then pulled out a sharp object, possibly a box cutter. The clerk handed over an undisclosed amount of cash and the suspect fled. He was seen getting into a silver SUV.
No one was injured.
Investigators say there have been no similar crimes in the area recently and the last time that Wawa was robbed was five years ago.
It's a busy location even overnight. Radnor Police are hoping someone will make a tip call.
Police further describe the suspect as having brown hair and was unshaven. He talked in a calm tone.
Anyone with information is asked to call 610-688-0503.