The incident happened on the top floor of the double decker bus between St. Aubin and Bel Royal, as it travelled from the Airport to town.
The bus is reported to have been full at 23:45 when the incident happened.
Police want to hear from those involved in the fight and anybody who witnessed it.
Islanders with any information can contact Police on 612612 or make an anonymous report to Crimestoppers on 0800 555 111.