Police say it happened around 1:40 p.m. at Rite Aid on Hillcrest Road.
They say the robber was described as a white man and implied he had a handgun. Police say he escaped in a white van heading south on Burhans Boulevard.
The suspect is described as wearing a white hoodie and blue jeans.
Anyone with information regarding this crime is asked to contact the Hagerstown Police Department at (301)-790-3700.