The chamber measures just 1.2 metres in length and no more than 0.8 metres in width, which makes it an unusually compact example of a monument type that already tends toward the intimate. Portal tombs, sometimes called dolmens, are among the oldest human-built structures in Ireland, typically dating to the Neolithic period. They consist of upright stones forming a chamber, with one or more large capstones laid across the top. At Carrickacroy, the entrance faces north, framed by two tall portal-stones with a low sill stone between them, a feature that would have controlled access to whatever lay inside.

The western portal-stone still stands, reaching 1.3 metres in height. Its counterpart on the eastern side has fallen and now lies flat, though it would originally have matched the standing stone in scale. The sides and back of the chamber are formed by single slabs, each standing roughly half a metre lower than the portal-stones, which gives the structure its characteristic wedge-like silhouette when viewed from the side. The backstone is gable-shaped and tilts inward toward the chamber's interior. What may once have sealed the whole structure, the roofstone, has been displaced and lies prostrate to the east. Ruaidhrí de Valera and Seán Ó Nualláin recorded the tomb in their Survey of the Megalithic Tombs of Ireland, published in 1972, where it appears as number 35 in their Cavan catalogue.