The mound, measuring roughly six metres by five and a half, holds the disturbed remains of a prehistoric tomb, one that has been partly dug out and robbed of its southern side. What survives is fragmentary but legible: a single backstone to the east, a double side-wall to the north, and a probable outer walling stone exposed to the northwest. The scattered stones along the southern edge of the mound are likely the displaced remnants of the missing wall.

Wedge tombs are the most numerous class of megalithic monument in Ireland, built broadly during the late Neolithic and into the Early Bronze Age, perhaps between 2500 and 2000 BC. They take their name from their characteristic profile, wider and higher at the front, tapering toward a closed back end, and they are found in unusually high concentrations along the Atlantic seaboard, particularly in counties Clare, Galway, and Mayo. The Eyrephort example is small, its chamber measuring just 1.8 metres in length, and its alignment running northwest to southeast. The classification itself remains tentative; the damage done to the structure makes a firm identification impossible, though the surviving elements fit the wedge-tomb form well enough to make that identification the most likely one. George Petrie, the nineteenth-century antiquarian and artist who documented much of Ireland's early monument record, noted the site, and his observation from 1972 remains the principal published reference for it.