The damage, equating to £54, was done at Bondgate Hall, on Bondgate Without, overnight on Saturday.
Alnwick Police Inspector Paul Truscott said there are no suspects at present, so anyone with information should call police on 101.
Vandals smash window of listed building in Alnwick
Vandals smashed a window of a Grade II*-listed building in Alnwick.
By The Newsroom
Tuesday, 15th March 2016, 3:44 pm
Updated Tuesday, 15th March 2016, 3:51 pm