The crash happened at around 12pm on March, 22, on the B725 Dumfries to Glencaple road.
It involved two cars, a silver Vauxhall Corsa, driven by a 21-year-old woman, and a white Honda Jazz, driven by an 86-year-old man.
The man was taken to Dumfries and Galloway Royal Infirmary where he later died.
The woman was taken to the same hospital with serious injuries.
The road was closed for eight and a half hours to allow for investigations and was reopened at 8.30pm on Monday.
Sergeant Billy Broatch, of Dumfries and Galloway Road Policing Unit, said: “Our thoughts are with the family and friends affected by this incident.
“We are carrying out extensive investigations into the incident and we would like to speak to anyone who witnessed the crash to establish the exact circumstances.
“In particular we would like to speak to anyone who may have dash-cam footage that could help with our enquiries to get in touch."
If you have any information on the incident you should call Police Scotland on 101 quoting incident 1372 of March, 22.