Alexander O’Haire, 79, was taken to Dumfries and Galloway Royal Infirmary after the collision last Friday afternoon.
But police have confirmed that he died in hospital on Sunday.
Mr O’Haire was from Braco Farm at Shawhead, not far from where the smash occurred at a junction leading to Arnmannoch, Shawhead at about 3.45 pm.
It involved a grey Volkswagen Beetle being driven by Mr O’Haire; a black Vauxhall Corsa driven by a 22-year-old woman; and a white Ford Transit van, driven by a 65-year-old man.
The Corsa and the van driver were both taken to hospital for assessment and later released.
A police investigation into the cause of the smash is continuing and officers are appealing for witnesses.
Sergeant Jonathan Edgar, of Dumfries road policing unit, said: “Given the time of day, there would have been a lot of traffic on the road so we’re appealing for anyone who saw the collision to contact us. Equally, we’re looking to speak to people who stopped to assist or had dash cameras fitted to their vehicles around the time of the collision.
“If anyone has any information, please contact us on 101 quoting incident number 2443 of 25 October 2019.”