The incident took place on Saturday November 12 2016 outside the Spey Lounge on Leith Walk.
The attack occurred around 1.20am when a 22-year-old man was knocked unconscious and sustained multiple fractures to his head.
Detectives are keen to trace the man pictured within the CCTV footage, who was in the bar prior to the assault.
The man is described as white, of medium build, around 20-25 years old, 5ft 8 – 10ins in height and with short fair hair.
At the time of the incident, he wearing a dark Nike hooded top and blue jeans.
Anyone who recognises the man in the images is asked to contact police immediately.
DC Ryan Lee of Gayfield CID said: “The victim was subjected to an unprovoked and sustained assault during which he suffered multiple fractures to his head.
“The man pictured is believed to be of significance to our investigation and anyone who can assist in tracing him is asked to come forward.
“Similarly we would ask the man himself to get in touch with police and help with our investigation.”
Those with information can contact Police Scotland on 101 or the charity Crimestoppers in complete anonymity on 0800 555 111.