The local authority posted a picture of the Harrow and Wealdstone disaster which happened 37 years later.
Events are taking place in Gretna to mark the 100th anniversary of the Quintinshill crash on 22 May 1915.
The council apologised for the "oversight" and said the picture had now been changed.
The error was pointed out to the BBC Scotland news website via its south of Scotland Twitter feed.
More than 200 people died - most of them soldiers - in the accident during World War One near the Scotland-England border.
The Harrow and Wealdstone crash claimed more than 100 lives in 1952.
Dumfries and Galloway Council has apologised over using an image of the wrong accident on website details of events to mark the Quintinshill crash.