The robbery happened at Applegreen Service Station, on the A49 Crossways in Church Stretton, at about 9.50pm on Friday.
The thief entered the premises off Crossways with a hammer and threatened staff before taking money and cigarettes.
He is described as white, wearing a blue puffer jacket with a hood and blue tracksuit bottoms.
West Mercia Police said staff were left shaken but otherwise uninjured.
Detective Sergeant Darren Stacey, from Shropshire CID, said: “This was obviously a traumatic and horrific incident for the victim and we’re keen to hear from anyone who may have any information that can help with our enquiries.”
Anyone with information can contact police on 101 or at westmercia.police.uk quoting incident reference number 711_I of September 25, 2020.
Alternatively, contact Crimestoppers anonymously on 0800555111 or crimestoppers-uk.org