It is roughly circular, measuring about 35 metres across, and its interior is grass-covered and tilts gently down toward the north-east. An earthen bank defines the perimeter, though it is uneven in its survival: reasonably substantial on the northern and eastern sides, where it still rises to around 1.45 metres above the outer ground level, it has been reduced on the western side to little more than a scarp and a hedge. There is no visible fosse, the external ditch that would typically accompany an earthen ringfort, and no identifiable original entrance anywhere along the circuit.

This kind of enclosure belongs to a broad category of earthen ringforts, known in Irish as a ráth, which were the most common form of rural settlement in early medieval Ireland, generally dated between the sixth and twelfth centuries. They were typically the enclosed farmsteads of a family or small community, defined by a bank and fosse to contain livestock and mark territory rather than to provide serious military defence. The absence of a fosse at Mullabrack is notable, since most examples of the type were dug out as much as they were built up, the excavated material forming the bank. Whether that ditch was always absent here, or has simply been levelled and absorbed into the surrounding land over the centuries, is impossible to say without excavation. The bank itself varies considerably in width and height around the circuit, suggesting differential survival rather than an original asymmetry in construction.