A 24-year-old man was assaulted in Fotheringhay Road, Corby.
The victim had left The Kingfisher pub and was walking towards Willowbrook Road when he was approached by a man who punched him in the face.
The man fell and hit his head on the ground but was not seriously injured.
The attack happened between 1am and 1.20am on Saturday but the victim was unable to give police a description of his attacker.
Anyone with information, or who saw the incident, is asked to contact the police on 101 or Crimestoppers on 0800 555 111.