Staff at a Co-op store in Portslade were held up by two robbers who made off with cash from the tills and safe.
Three women were working in the Abinger Road shop on Monday night (February 13) when the two men arrived at 9.50pm.
Police said one of the staff members was pulled by the hair to a safe and forced to open it at knifepoint.
The other man broke open tills before both men escaped to a waiting red Volkswagen Golf, driven by a third person.
Both men were dressed in dark clothing and wearing balaclavas, according to police.
Sussex Police said: “The incident was extremely upsetting to all the staff.”
Witnesses or anyone with information about the robbery is asked to email firstname.lastname@example.org with the reference 1313 of 13/02. You can also report online or call 101.