Portal tombs, sometimes called dolmens, are among Ireland's oldest megalithic monuments, typically dating to the Neolithic period and consisting of two upright portal stones framing a chamber entrance, capped by a large covering stone. At Killaclohane, what remains is skeletal but legible: two leaning portal stones set roughly 0.90 metres apart, aligned north to south with the entrance facing downslope toward the north, and a roofstone that measures nearly four metres long, two and a half metres wide, and some 0.80 metres thick, a substantial slab by any measure.

The two portals both lean markedly to the east, and their original heights, if they were ever fully erect, would have been approximately 1.60 metres and 1.70 metres respectively. The chamber they once enclosed was probably around two metres long. A split boulder slab found in the chamber area was moved to its present position from the rear of the structure at some point, according to the landowner, though whether it ever formed part of the original tomb is uncertain. What is clear is that the monument spent a long period incorporated into an ordinary field fence. A drawing made by Commander O'Connel in March 1939 shows the structure absorbed into this boundary wall, which abutted the south end of the roofstone and the east face of the east portal. That fence was removed in early 1993, leaving a low scatter of earth and stone along the monument's east side. There is no surviving evidence of a cairn or mound that would originally have covered the chamber, as was common with monuments of this type.