The man was walking at the junction between Galloway Street and Glasgow Street at 21:30 when he was struck by a green Vauxhall Adam.
He was taken to hospital in Dumfries before being transferred to Edinburgh Western Infirmary.
Staff have described his condition as serious.
Police have asked anyone who saw the incident to contact them.
A 19-year-old man is being treated for serious injuries after being hit by a car in Dumfries town centre on Christmas Eve.