Lincolnshire Police are appealing for witnesses to a serious assault outside the Rock Shop on Lumley Road in Skegness near to the LA Café.
The fight at around 1.20am on Friday, August 18, has left one man in his 20s in hospital in a serious but stable condition.
A second man in his teens has been arrested and released under investigation.
The brawl involved a group of two men and three women.
Anyone who witnessed the fight should call police on 101, quoting incident number 27 of August 18.
Alternatively, contact the independent charity Crimestoppers anonymously on 0800 555 111.