A teenager was allegedly kicked off his bike and punched and kicked as he lay on the ground.
Police say the 14 year old suffered minor injuries to his head and face during the assault.
It happened near at the pedestrian crossing near St Helier Grand Marche at around 7.30pm on Saturday (5th October)
The attacker, who is also 14, had short dark hair and was wearing a black hooded top and dark jeans.
Police want to speak to any witnesses.
"Anyone who may have seen this or who has any information is asked to contact police on 612612 or the independent charity Crimestoppers anonymously on 0800 555 111 or via their Anonymous Online Form at Crimestoppers-uk.org"

Report reveals what islanders are earning
Jersey's Siena Stephens gets Supertri wildcard
Spaghetti and ale on the menu at Gorey Fete
Police seek information after assault sent 61-year old man to hospital
Economic Development Minister apologises for minimum wage comments
Jersey's GCSE pass rate rises to 77.1%
'Après-ski' bar and curling rink coming in the autumn
£310k given to families to help with back-to-school costs