Local information suggests it was moved in relatively recent years from a spot a short distance upslope in the same field to its current position within a levelled cashel, a term for a stone-walled enclosure of early medieval origin. Whether the slab ever belonged to that cashel, or simply ended up inside its remains by convenience, is an open question.

The carving itself repays close attention. The cross sits towards the upper portion of the slab, pecked out in shallow false relief within a rectangular panel, with a shallow horizontal groove marking the top of that panel. The arms curve outward gently to expanded terminals, meaning that each arm flares slightly at its end rather than terminating in a flat edge, and a small stem or projection, only a couple of centimetres wide, descends from the foot of the cross. Measured precisely, the cross is not quite symmetrical: the upper vertical arm and the right-hand horizontal arm run slightly longer than their counterparts, a small human irregularity in an otherwise carefully executed piece. The scholar Michael Herity, writing in 1989, proposed a seventh-century date and drew comparisons with a cross-slab on Caher Island, also in County Mayo, and with a cross carved on an ogham stone on Mount Brandon in County Kerry, the Kerry example also carrying the distinctive short stem at the foot. Ogham stones are standing stones bearing an early Irish script inscribed along their edges, and the fact that comparable cross forms appear on both manuscript illuminations and carved stones of this period suggests the Dadreen slab belongs to a wider, connected world of early Christian visual culture in the west of Ireland.