The fort at Mullaghnameely measures roughly 32 metres across its east-west axis, and its defining feature, beyond the shape itself, is the way the landscape has conspired to erase it unevenly. The bank that once enclosed the interior survives on the eastern and western sides to an external height of about a metre, but on the northern side it has been worn down to little more than a low scarp. Outside that bank runs a fosse, a shallow defensive ditch, still traceable to a width of three to four metres across its top, though it has silted and settled to a depth of only around 0.4 metres.

The entrance, just 1.6 metres wide, opens to the east, approached by a causeway four metres across that would once have carried traffic over the fosse. This arrangement, a narrow formal gateway with a raised causeway, is typical of the ringfort tradition in Ireland, enclosures built predominantly during the early medieval period, roughly the fifth to twelfth centuries, and used as enclosed farmsteads or higher-status residences by local families and petty lords. What makes the Mullaghnameely example quietly awkward is what has happened to its southern side. A field bank running east to west, which also marks the townland boundary, cuts directly across the monument. South of that line, the fort simply does not survive; the boundary has swallowed it. The recorded dimensions, 29 metres east-west and 19 metres north-south internally, reflect only what remains above ground. The full original extent is a matter of inference rather than measurement. Michael J. Moore documented the site in the Archaeological Inventory of County Leitrim, published by the Stationery Office in 2003, and that record remains the primary basis for what is known about it.