The 53-year-old Shipley man had been visiting a friend in Harewood Avenue on Saturday evening and left to catch a taxi at about 1am on Sunday.
He failed to meet the taxi and returned to the house at about 4.30am with injuries to his head and face.
He was taken to hospital, but his injuries were not thought to be serious.
Detective Inspector Neil Benstead, of Bradford District CID, said: “We would like to speak to anyone who might have witnessed this attack, or who saw a group of men in their late teens/early 20s in the Harewood Avenue area at around 1am on Sunday.
“Anyone with information is asked to contact Bradford District CID on 101 or Crimestoppers on 0800 555111.”