The castle's rectangular tower, measuring roughly 18 feet high by 16 feet wide, occupies a naturally defensive position on limestone rock, surrounded by bogland that once made approach difficult. A wide fosse, or defensive ditch, encircles the northern base of the knoll, whilst a watercourse curves around the castle rock; this may have been deliberately excavated as a leat to create an additional moated defence. Today, only fragments of the north and south walls remain standing, their ivy-covered stones reaching about 18 feet skyward, whilst the foundations of the other walls have vanished entirely into the landscape.

The castle's history weaves through centuries of Irish conflict and ownership disputes. In 1578, it was held by the Knight of Glin, but by the late 16th or early 17th century, it had passed into the hands of rebel Thomas Came, when it was known as Cowleshonikyne. The 1654;56 Civil Survey of Limerick reveals that Thomas FitzGerrald of Glin and alderman Nicholas Fanning owned the land containing "two good houses, and Cottages", and the 1657 Down Survey map depicts two buildings standing side by side in Ballyshonickbane, suggesting the site remained significant even as the castle fell into ruin.

Early 20th century antiquarian Thomas Westropp documented two ivy-covered ruinous buildings atop the rock in 1906;7, and whilst modern aerial photography shows the site obscured by woodland, the castle's remnants continue to mark this strategic location. Positioned precisely at the townland boundaries, with Drominclara 75 metres to the north and Tobermurry 180 metres to the east, Carriganea Castle remains a tangible link to the complex territorial divisions and defensive strategies that shaped medieval and early modern Limerick.