The States police say four men set upon three others at the junction of New Street and Union Street at about 12.40am on Saturday.
An 18-year-old was taken to hospital with facial injuries.
Four men – three aged 19 and one aged 21 – were later arrested on suspicion of grave and criminal assault and have since been released on police bail.
One of the suspects was wearing a black jumper with a white horizontal stripe and the word ‘GIVENCHY’ written on it.
Another was wearing an all-grey tracksuit. Anyone with information is being asked to phone the States police on 612612 or Crimestoppers on 0800 555 111.