The 53-year-old victim was in Waukglen Avenue in the Darnley area of Glasgow when a black car pulled up beside him.
The passenger of the car, which may have been an Audi A3, got out and attacked him with a metal pole while the driver also got out of the vehicle.
After the attack the pair got back into the vehicle and drove off.
The victim was taken to the Queen Elizabeth University Hospital where he was treated for serious facial injuries and later released.
Police are appealing for information about the incident which happened at around 3pm on Friday June 22.
Detective Constable Mark Hendry said: “We have yet to establish a motive for this attack and the man involved has sustained a serious facial injury.
“I am appealing to anyone who was in the area around the time of the incident to get in touch, any small piece of information regarding the suspects or the car could prove vital to our ongoing enquiries, helping us establish exactly what has happened and why.”
The suspect who was armed with the pole is described as white, with short receding hair and was wearing a grey hooded top and black Lacoste tracksuit trousers.
Police have been carrying out door to door enquiries and detectives are checking CCTV footage from in and around the area for any more information.
Anyone with information is asked to call officers at Helen Street Police Station via 101, quoting incident number 2875 of Friday June 22, 2018 or call Crimestoppers where information can be given anonymously.