It happened Saturday evening at the Cash Point ATM on Dunn Road in Eastover.
The victim told investigators the robber put a knife to her throat, took her money and took off in a white Toyota Camry.
Detectives say the suspect is a white male, possibly in his mid 40's. He was last seen wearing camouflage pants with a dark colored sweatshirt and baseball style cap.
Anyone with information is asked to contact the Cumberland County Sheriff's Office at (910) 323-1500.