According to the report of the 1622 commissioners, Castle Balfour was a "strong and beautiful castle of stone and lime… 100 ft long, 41 ft broad, most of the lower rooms being strongly vaulted"

Constructed of limestone and sandstone, it comprises a main block of 3 storeys with attics, with a large wing projection to the East and West. This plan is unmistakably Scottish in character.

Like many of the Plantation castles in County Fermanagh, the architecture is Scottish ‘strong-house’ in style with several turrets and corbelled projections. The building is thought to be the work of Lowland Scots masons as opposed to most of the other plantation castles which were built by local Irish tradesmen.