Two men were attacked in Club Amadeus in Northallerton at around 2am on Sunday 19 July 2015 .
One was taken to hospital with serious injuries. The other received a black eye and a chipped tooth.
It is believed the assault was unprovoked.
CCTV has been released of a man police want to speak to about the assault, he was ejected by door staff.
PC Caroline Pugh, of Northallerton Police, said:
If you are the man pictured in the CCTV, or you know who he is, you may be able to assist the investigation, and we would like you to come forward with any information.
Anyone who can help officers with their enquiries is urged to contact North Yorkshire Police on 101, select option 2, and ask for PC 1842 Caroline Pugh, or Northallerton Police.
If you prefer not to give your name, Crimestoppers can be contacted anonymously on 0800 555 111.
Please quote reference number 12150123363 when passing information about this incident.