Police said a robber entered the Subway on Moye Boulevard and demanded money.
The robbery happened around 9:30pm Friday.
It is unclear what kind of weapon was used.
No customers were inside at the time of the robbery, and no one was hurt, said police.
Investigators said the suspect left with an undisclosed amount of cash.
The robber is described as a light-skinned black man, about 6'2" with slender build, said police. .
Investigators said he was wearing a black ball cap and glasses, and he is described as having a tear drop tattoo under one of his eyes.
Anyone with information is asked to call the Greenville Police Department.