From the west and north it presents steep, reasonably defined sides; from the south, vegetation has blurred its edges almost entirely, and a field wall cuts across its eastern margin. It measures roughly fourteen metres north to south and nine metres east to west, rising to a maximum height of just under a metre. That modest profile is typical of a barrow, a prehistoric burial mound, a form that appears across Ireland in various shapes and sizes, some containing cremated remains, some inhumations, and some yielding nothing recoverable after millennia in the ground.

The mound at Poulnagun was marked as a barrow on Robinson's map of 1977 and formally listed under that classification in the Record of Monuments and Places in 1996. What gives the site a little extra interest is its relationship to a nearby monument: a stepped barrow sits approximately two hundred and twelve metres to the west-southwest. A stepped barrow is a variant form in which the mound is constructed in distinct tiered stages rather than rising in a smooth profile, and the presence of two different barrow types within a short distance of each other on the same ridge suggests the area held some significance for the communities who built here. Both monuments command wide views, particularly to the southwest, which may or may not have mattered to the people who chose this elevated ground, though ridgeline placement is a recurring feature of prehistoric burial monuments across the island.