A 54-year-old Lincoln man was left requiring hospital treatment after being assaulted by another man at the George and Dragon pub in the city.
The incident was reported to Lincolnshire Police at around 12.28am on Saturday, May 30 when a fight broke out inside the pub on the High Street.
The injured man suffered a cut to his head and was treated in hospital before returning home.
Officers investigating the incident would like to hear from anyone inside the premises who may have witnessed the assault, or anyone who has any information in relation to the enquiry.
People are being asked to contact Lincolnshire Police on 101 quoting incident 12 of May 30.
Police are also investigating a brawl at the nearby Shakespeare pub on the High Street on Friday evening at around 6pm.
A number of people were treated for minor injuries at Lincoln County Hospital following the altercation.
Anyone who saw the incident should contact the force on 101 quoting incident number 351 of May 29.
Alternatively, people can contact Crimestoppers anonymously on 0800 555 222.