The incident happened at the Sainsbury’s store in Talbot Road at around 6.20am last Thursday.
The victim was withdrawing cash when a man lunged at him and punched him to his head before taking £20 in cash.
He made off from the scene towards Cookson Street.
Detectives are keen to speak to the man pictured in CCTV images in connection with their enquiries.
The robbery happened on the same day as a cashpoint robbery in Fleetwood in which an elderly woman had £300 taken from her.
That incident happened at around 9.50am at the Santander branch in Lord Street
DS Simon Pritchard of Blackpool CID said: “While we are not linking the two robberies at this stage, they happened within a few hours of each other and we are keen to hear from anyone with any information about either of them.
“We would like to speak to the man pictured in connection with the Blackpool incident and I would urge anyone who recognises him to get in touch with us as soon as possible.”
Anyone with information can contact police on 101 quoting crime reference WA1609735.