The dolmen consists of a twelve-foot, thin, slab-like, tabular capstone supported by two slender portal stones, which support the capstone 1.8 m (6 ft) from the ground, creating a chamber in a 9 m (30 ft) low cairn. The cairn helped stabilize the tomb chamber, and would have been no higher during the Neolithic. The entrance faces north and is crossed by a low sill stone.
A crack was discovered in the eastern portal stone in 1985. Following the resulting collapse, the dolmen was dismantled, and the cracked stone was replaced. Excavations during that time found that between 16 and 22 adults and six children were buried under the monument. Personal items buried with the dead included a polished stone axe, a bone pendant, quartz crystals, weapons and pottery. In the Bronze Age, around 1700 BC, a newborn baby was buried in the portico, just outside the entrance. With its dominating presence on the limestone landscape of the Burren, the tomb was probably a centre for ceremony and ritual until well into the Celtic period, or it may have served as a territorial marker in the Neolithic landscape.
Due to the Burren's excellent dark skies and Poulnabrone's remote location, the car park, built in 2007, has been used by Shannonside Astronomy Club as an unofficial public observatory. In April 2013, many observations of the comet PanSTARRS C/2011 L4 were made by the club at this location.