The crime happened about 4 a.m. Friday at 1605 Pulaski Highway (U.S. 40).
The robber handed a note demanding cash to a clerk and she turned over an undisclosed amount of money. The robber implied he had a weapon but none was displayed.
He fled and no one was injured.
Police said the man was described as white, 25-35 years old and 5-feet-8 to 5-feet-10. He was wearing a gray and black jacket, blue jeans and a baseball cap.
Anyone with information is asked to call troopers at 302-365-8566.