The mound is circular and round-topped, measuring roughly 22 metres across and standing nearly three metres high, which makes it a substantial presence even in its current, overgrown state. A hollow at its centre betrays the fact that cairn material has been removed at some point, a common enough fate for such monuments, where loose stone proved too tempting for later builders.

This is a passage tomb, a type of Neolithic burial monument in which a stone-lined corridor leads into a central chamber within a cairn, typically dating to somewhere between 4000 and 3000 BC. At Slievethoul, four upright stones, known as orthostats, remain in position, and the chamber runs on an east-west axis. The vegetation is now too dense to identify any kerbstones, the upright stones that would originally have defined the outer edge of the cairn, though Michael Herity, writing in 1974, noted a single granite boulder visible near the base at the northern edge. The monument is not alone on the hill; a second passage tomb lies approximately 300 metres to the east-southeast, suggesting this summit once held some significance in the Neolithic landscape of the Dublin upland fringe. The site has been protected under a preservation order since 1940, issued under the National Monuments Acts.

The tomb sits within Slievethoul Woods, and reaching it involves navigating the woodland to the summit clearing. Given that the notes compiled by Geraldine Stout and Padraig Clancy describe the site as too overgrown to read clearly, visitors should expect to work a little to make sense of what they are seeing. The four standing orthostats are the clearest indication of the chamber's original layout. The companion tomb to the east offers a useful point of comparison if you are trying to understand how these monuments once related to one another across the hilltop.