The outcrop stretches about 4.6 metres in length and is divided by a natural fissure and a downward step into three panels. Two of those panels are covered with an elaborate vocabulary of carved marks: cupmarks, which are simply small rounded depressions pecked into the stone surface, surrounded in many cases by one, two, three, four, five, or even six concentric rings. There are around thirty-one cupmarks in total, along with sixteen cup-and-ring motifs of the single-ring type, many of them penannular, meaning the ring is left deliberately open with a short radial groove running from the central cup and out through the gap. The largest single motif on the southern panel is a cup encircled by six rings, its outermost ring only partially complete, with a triangular groove fanning outward from the central cupmark toward the edge. On the western end of that same panel, a cluster of marks has been interpreted as a possible human figure, perhaps someone drawing a bow, though the reading remains tentative.

The question of when all this was made has no settled answer. The scholar Emmanuel Anati, writing in 1963, proposed that varying degrees of wear across different motifs suggested the carvings were added over an extended period rather than in a single episode of work. A later commentator, Finlay, offered in 1973 the more cautious observation that differing wear could equally reflect different carving techniques rather than different eras of activity. Rock art of this type, broadly associated with the Later Neolithic and Early Bronze Age in Atlantic Europe, was not a single tradition with fixed rules: motifs were sometimes added to existing panels across generations, and the same forms appear across Ireland, Britain, and Iberia without any consensus yet on what they meant to the people who made them. The Derrynablaha boulder sits within the wider landscape of the Iveragh Peninsula, looking north over the Ballaghbeama Gap and east toward Lough Brin, a position that feels deliberate, though whether that orientation carried any significance for the carvers is unknown.

The boulder sits in rough mountain pasture and is accessible on foot, though the slope is steep. The carvings are described as clearly visible on both decorated panels, which lie at a gentle angle and catch light from the north-northwest. A small stone adjacent to the western end of the northern panel has the appearance of a natural seat, which is either coincidence or something rather harder to explain.