Known as Grave 1, it is not found inside the cairn itself but on the bedrock surface immediately to the south-east of the structure's inner revetment, the ring of stones that defines the cairn's core. The body had been placed in a crouched inhumation, a burial posture common in prehistoric Ireland in which the body is drawn into a contracted position rather than laid out flat. This particular individual, an adult male, was positioned on his right side, facing west, and partially covered by horizontal limestone slabs. Nearby, five upright slabs were arranged to his north and north-east, four of them forming a rough row running north-west to south-east. Whether these constitute the remains of a cist, a small stone-lined grave box, is uncertain; the arrangement is irregular enough that scholars have remained undecided on the point.

The burial was excavated in the 1930s by the Third Harvard Archaeological Expedition in Ireland, led by Hugh O'Neill Hencken, who also restored the cairn following the dig. Radiocarbon dating, carried out by Brindley and Lanting and published in 1992, placed the burial between approximately 1486 and 1452 cal BC, placing it firmly in the mid-second millennium BC. This was not, it turns out, a solitary interment within a monument devoted to a single moment of funerary use. The dating aligns Grave 1 with what appears to have been a final phase of mortuary activity at Poulawack, during which several cist burials were also constructed within or around the cairn. Graves 2 and 3 belong to this same broad period, and Grave 7 may do so as well, though the evidence for its date is less conclusive. The poorly preserved condition of the skeletal remains, noted by Hencken at the time of excavation, limits what can now be said about the individual himself, but the placement of the body outside the main cairn structure, on the bedrock rather than within a formal cist, gives this burial a quietly unusual character among its neighbours.