That overlap of civic infrastructure and sacred space is not unusual in Irish medieval towns, but what makes this particular site worth a closer look is a small, easily missed detail on the outer face of the south-eastern corner of the boundary wall: a limestone window label stop, carved with vine-leaf and interlaced tendril ornament, lifted from an earlier architectural context and built into the upper courses of the enclosure. A label stop is the decorative terminating block at either end of a hood moulding above a window or door opening; this one closely resembles those still visible on the west porch window of St. Mary's itself, which suggests it was salvaged from the same building campaign before finding a second life in the boundary wall.

The graveyard, which measures roughly 105 metres north to south and 114 metres east to west, contains a number of seventeenth-century graveslabs, and several of those are themselves re-used, meaning the stone carrying one person's commemorative inscription was at some earlier point cut or repurposed from another. The churchyard was once considerably more busy with structures than it is today. On the southern side stood a vicar's house and a school. On the eastern side, according to Robert Simington's 1931 survey of civil survey material, there was a slate-stone building that served as a hospital, described at the time as being for the "old impotent decayed inhabittants of Clonmell", a phrase that carries its own particular weight, the word "impotent" used in its older sense of physically incapacitated or powerless rather than its modern meaning. The presence of a hospital, a school, a vicar's residence, and a working church within a single enclosed space gives a sense of how much of a town's daily life, practical as much as spiritual, was once organised around the parish churchyard.