The Scottish band, whose hits include Always The Last To Know and Kiss This Thing Goodbye, will headline on Saturday July 26.
Organisers said it will mark the group's first festival appearance in 12 years.
They have already revealed that rapper Dizzee Rascal will perform on the Friday, along with The Feeling, The Zombies and Big Country.
Motown legends Martha Reeves And The Vandellas will also appear as part of their tour to mark the 50th anniversary of their biggest hit, Dancing In The Street.
The festival takes place at East Kirkcarswell Farm in Dumfries and Galloway, where the classic 1973 Wicker Man film was made.
It culminates with the burning of a 40ft wickerman.
Now entering its 13th consecutive year, there will be 10 stages with a mixture of leading artists, alternative acts and up-and-coming talent.
Del Amitri guitarist Iain Harvie said: "It's been a long time, but what a prospect it is to play to a Scottish festival crowd again. We're really looking forward to joining all the Wicker fans this summer."
Festival co-ordinator Helen Chalmers said: "We are over the moon that Del Amitri have chosen Wickerman to make their Scottish festival comeback, after such a distinguished and memorable career it'll be amazing to see the original members performing live again."