The incident happened in the Moko Lounge during the early hours of Wednesday 5 December 2012
A group of men and possibly women, numbering between five to eight people in total, were involved in the altercation.
A 22-year-old local man suffered a large cut to his forehead which required hospital treatment.
Two men aged 24 and 18, also from Harrogate, were arrested in connection with the investigation. They have been released on police bail pending further enquiries.
Officers have spoken to a number of people who were in the club on the night in question.
They are also appealing for any other witnesses or people with information regarding incident to come forward to assist.
If you can help, please contact North Yorkshire Police on 101, select option 2, and ask for Harrogate CID.
Alternative, information can be passed on anonymously to Crimestoppers on 0800 555 111. Please quote reference number 12120204645.