The victim, a 30-year-old local man, suffered a broken eye socket and two black eyes when he was attacked while standing alone at the bar in the Devonshire Arms, on Skipton Road during the evening of Friday 17 January 2014.
Following the assault the victim and his female friend left the pub.
Officers are appealing to anyone who witnessed the incident to contact them with information.
PC Steve Dougall, of Harrogate police, said: This appears to have been a totally unprovoked attack which left the victim with some nasty injuries to his face.
I am appealing to anyone who was in the pub at the time of the incident, or anyone with information that can help identify who was responsible to get in touch.
Anyone who can help officers with their enquiries is urged to contact North Yorkshire Police on 101 – select option 2 – and ask for Steve Dougall or Harrogate police.
Alternatively, information can be emailed to email@example.com
If you prefer not to give your name, Crimestoppers can be contacted anonymously on 0800 555 111.
Please quote reference number 12140010029 when passing information about this incident.