A man armed with a hammer threatened staff and stole cash from a Tesco Express shop in Bicester last week.
Thames Valley Police said the man burst into the store on Holm Square, Southwold at 11.05pm last Wednesday.
Officers have since released a CCTV image of a man who may have information that helps their investigation.
Investigating officer Detective Constable Anneliese Palfrey, of Force CID based at Bicester police station, said: “We are appealing for information following this robbery and we have released CCTV images of a man we believe might have information in connection with this incident.
“We believe that shortly before the incident, at around 11pm, the offender hid behind a bin before going into the shop.
“We would ask anyone who has information or may have been passing by between 11pm and 11.10pm to please come forward.”
Contact police on 101 if you have any information.