A southbound Volkswagen Crafter Van collided with a Peugeot Partner Van on the A702, just north of Candymill Road, near Biggar, at 17:35 on Thursday.
A 58-year-old male passenger in the Peugeot is in a serious but stable condition in hospital.
The 32-year-old driver was uninjured as was the 26-year-old male driver of the Volkswagen van.
Police said both vehicles suffered extensive damage in the collision and the road was closed for several hours while officers investigated the scene.
Police have appealed for witnesses to a crash between two vans which closed a Lanarkshire road for several hours.