The assault happened at around 23:30 on Friday 16 October at the Town bar.
Information gathered to date by investigating officers indicates that one man, who was dressed in a long sleeved grey top, was arguing with another, who was dressed in a “mustard yellow” top.
It is alleged that things got heated and a glass was thrown. It connected with another man in the vicinity, causing him facial injuries. The extent of those injuries has not been described by police.
As the investigation continues, officers are appealing for anyone who witnessed the incident to contact PC 142 Hewlett at the Guernsey Police Station on 01481 222 222.
Alternatively, people can contact CrimeStoppers anonymously on 0800 555 111.