The 33-year-old was struck on the face with a weapon during the assault by a group of men in Keir Hardie Road, Larkhall.
The attack happened on Friday at about 8.30pm and the men, all aged 20-30, then fled.
The victim was treated in hospital for a serious facial injury and later released.
Police believe the attack was planned and have appealed for witnesses to come forward.
Detective Constable David Timmons of Hamilton CID said: "We're continuing our inquiries into this attack, however, I would stress that at this time the attack is not believed to be random."