The alleged assault took place last Tuesday (30 January) at 16:00 at Newgate Street Newsagents in St Helier.
The victim reported being struck twice, once to his chest and once to his face. He did not require medical treatment.
Police said the two men involved did not know each other.
They are now on the lookout for a suspect wearing a light grey beanie hat, bright red waterproof jacket, dark blue jeans and white trainers who may have been holding a water bottle at the time.
CAN YOU HELP?
Anyone who may have seen this assault or can aid in identifying this person are asked to contact police on 612612 or the independent charity Crimestoppers anonymously on 0800 555 111 or via Crimestoppers-uk.org.