The surface, roughly four metres by three and a half, slopes gently upward to the west, and concentrated near its southern end is a dense arrangement of cup-and-ring carvings: circular motifs pecked into the rock, consisting of a central hollow, the cup, surrounded by one or two concentric rings. There are at least nine single cupmarks, five examples with one ring, and three with two rings, one of which has a deliberate gap in its outer ring. An incomplete oval sits beside one of the cupmarks, lightly pocked as though the carver abandoned the work partway through.

What makes the Derrynablaha boulder particularly interesting is what was hidden beneath the peat. Around the early 1960s, the removal of a layer of peat roughly forty centimetres deep from the northern end of the stone exposed additional carving that had been sealed under the bog: a bifurcated groove nearly two and a half metres long, and a pocked outline rectangle close beside it. These features had been documented by the researcher Anati in 1963 and later noted by Finlay in 1973, but for much of the stone's modern existence they were simply not visible. The carvings as a whole belong to the tradition of prehistoric rock art found widely across Atlantic Europe, generally attributed to the Neolithic or Early Bronze Age, though the specific meanings or functions of cup-and-ring motifs remain genuinely unresolved. The stone sits at around 106 metres above sea level, with a stream running about fourteen metres to its north.

The rock art is set in rough heath pasture, accessible via a farm roadway running close to the eastern side of the boulder. The carvings are heavily weathered and shallow, with rings typically only a centimetre or so wide and marks just a few millimetres deep, so low, raking light in the early morning or late afternoon gives them the best chance of being legible. A second carved rock sits immediately to the north, making this a small but notably concentrated area of prehistoric carving on the south Kerry uplands.