A man was taken to hospital after an alleged fight in St Helier in the early hours of Sunday morning.
Police said an altercation between two men occurred outside the Minden Place car park toilets at around 02:30 on 24 August.
One of the men was “seriously assaulted” and required hospital treatment, according to the force.
A man has been arrested on suspicion of assault and an investigation is underway.
Police are now appealing for information regarding the incident.
Both men involved are described as white, aged between 30 and 40. One was wearing a white shirt and grey shorts, while the other was dressed in a blue T-shirt and jeans.
Police are particularly keen to speak to two women who were believed to have been in the Minden Place toilets prior to the altercation.
Anyone with information has been asked to contact police on 612612.
They can also make an anonymous report through the charity Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.