It happened outside “Chick-o-land” in Winchester Street between 3.30 and 3.40 am on Sunday July 20.
A 21-year-old man from Southampton was with a group of friends when he became involved in an argument. He was punched in the face twice and fell to the ground, hitting his head.
He was then kicked in the head, and was unconscious for a short time-he was later treated for head injuries at the Royal Hampshire County Hospital.
The attacker made off towards the Asda supermarket.
He is described as:
• Of mixed race
• Wearing dark clothing
Anyone with any information is asked to police at Andover police station by calling 101 or call Crimestoppers on 0800 555 111, where information can be left anonymously.