Built from roughly coursed rubble and topped with a crenellated wall-walk, the structure dates to the late 16th century, though its current appearance owes much to later modifications. The original defensive features included a two-ordered door on the south wall with chamfered stops, protected by a machicolation at wall-walk level; however, only the bottom half of this doorway survives today.

The castle’s transformation began in earnest after O’Carroll Castle was captured by English forces in 1557 and subsequently granted to the Darby family in the 17th century. During this period, a Jacobean house was added to the north of the tower, expanding the complex beyond its original military purpose. The most dramatic changes came during the Georgian era, when the western face was completely remodelled with the insertion of a fashionable Georgian door and façade, whilst a new house was constructed around the core of the earlier buildings, fundamentally altering both the interior layout and external appearance.

The defensive bawn that once surrounded the castle on its southern, western and northern sides has been heavily modified by 18th-century landscaping and rebuilding work, with the eastern edge naturally protected by a cliff face. These alterations reflect the building’s transition from a defensive stronghold to a comfortable country residence, documenting the changing priorities and architectural tastes of its various owners across nearly five centuries of Irish history.