Dromore Castle appears to have been built on the instructions of Denis Mahony, his father John Mahony had made the decision to build a large home earlier in the 19th century, but apparently abandoned the attempt after his yacht, returning from London with lead for the roof and wine for the cellar, sank in the Kenmare River, in view of the site of the house. After this, no further work took place until architect Thomas Deane began building work for Denis Mahony in the 1830s. The Gothic revival style house was completed in 1839.
Denis Mahony was a minister of the Church of Ireland. He set up a soup kitchen at Dromore during the time of the Irish Potato Famine and preached in the chapel at Dromore to the hungry who came for food.
The 2013 film ‘The Lobster’ starring Colin Farrell and Rachel Weisz was set in the woodlands at Dromore and Parknasilla.