The incident happened at 1.10am on Sunday 13 October in Aruba Restaurant and Bar on Pier Approach.
A man accidentally backed into another man on the dance floor and was pushed away.
The victim, a 35-year-old Poole man, turned around and carried on dancing. The offender then punched him causing the victim to fall to the ground unconscious. He suffered fractures to his jaw as a result.
Detective Constable Katie Savill, of Bournemouth CID, said: “I am now able to release a CCTV image of a man I wish to speak with as I believe he can help me with my investigation.
“I need to establish what exactly happened as the victim sustained nasty injuries to his face.
“I would urge the man pictured – and anyone who recognises him – to contact me, in confidence, as soon as possible.”
Witnesses and anyone with information should call Dorset Police in confidence on 101 quoting incident number 13:39. Alternatively, call the free and anonymous Crimestoppers line on 0800 555 111 where mobile phone tariffs may apply.