The castle measures just 6.3 metres by 4.75 metres and rises three storeys high, though it likely once stretched a storey higher before time took its toll. Built from roughly coursed limestone rubble with a distinctive base batter, this probable seventeenth-century tower house was already described as an 'old little castle ye walls onely standing' in the Civil Survey of 1654-6, suggesting it had seen better days even then.

The castle's ownership tells a fascinating tale of changing fortunes in post-medieval Ireland. Before the 1641 Rebellion, the lands at Ballycolliton were divided amongst several proprietors, including Sir Nicholas White, who had purchased from Edmond Kenedy, John Hurly, who bought from Mortagh O'Brien of Annagh, and Rory Kenedy, who inherited from his ancestors. In 1677, William Cleburne acquired the castle along with surrounding lands from Captain Solomon Cambie. William's son, also named William and born in 1642, became known as 'William of Ballycollitan Castle'. Despite being a firm believer in the Divine Right of Kings, he married Elizabeth Cambie, daughter of a Cromwellian officer, though their only child died in infancy. When William died in 1684, he left instructions to be buried in Kilbarron Church under a plain marble stone engraved with his name and coat of arms; his estates passed to his nephew.

Today, the tower house retains intriguing architectural details despite nineteenth-century modifications that saw outhouses attached to three of its faces and a water tank and bellcote placed on its roof. The interior reveals a ground floor now filled with debris, a first floor with a fireplace in its eastern angle, and a barrel-vaulted second floor accessed via mural stairs. The second floor's large segmental-arched window embrasures still show their original wicker centring, though the windows themselves are now blocked. Various window styles throughout; simple flat, round and ogee-headed single lights; speak to different phases of construction and modification. A possible bawn wall or forebuilding attached to the northeast angle hints at the castle's former defensive arrangements.