The tomb sits in the south wall of a small chapel occupying the space between the chancel and south transept, and what makes it quietly arresting is the gap between the grandeur of its original conception and what survives today. A rounded arch with multifoil decoration rises beneath a large square projecting hood, supported by three corbels along its top edge, each originally crowned with a carved figure. Only the central corbel remains intact, bearing a carved angel above low-relief foliage; the other two figures, tentatively identified as a male and a female, are largely lost. The front panel of the tomb once showed all twelve apostles in low relief, but only half the panel and five figures remain. Three are identifiable with reasonable confidence as St James, St Andrew, and St Peter; a fourth, holding what appears to be a spear, has been tentatively read as St Thomas, who is conventionally depicted with that attribute. A fifth, St John, was still present in the early twentieth century and was photographed by art historian Edwin C. Rae, though it has since disappeared.

Tibbot na Long, whose nickname translates loosely as Theobald of the Ships, had a career shaped by the turbulent politics of the late Tudor and early Stuart periods. Following the defeat of the Spanish Armada, he was knighted for his support of Lord Mountjoy when Spanish forces landed at Kinsale, and in 1627 he was created the first Viscount Mayo. He married Maud, daughter of Charles O'Connor Sligo, and the couple had four sons and three daughters. He died in 1629, and a local tradition holds that he was killed near the abbey by his own brother-in-law, Diarmuid O'Connor Sligo, though scholars have suggested this story may conflate his death with an earlier killing recorded in the Annals of the Four Masters in 1505. He was the first of his line to be buried in the chapel, and subsequent Viscounts Mayo continued to use it as a family vault; the last interment was that of another Theobald, the seventh Viscount, in 1741. Two fragments of the original inscription survive and are now fixed to the wall above the tomb. They would once have read: "Here lies the body of Sir Tibbot na Long Bourke, First Viscount Mayo, in which all his posterity was buried, whereof four were Lords or Earls."

The abbey itself is open to visitors, and the sacristy where the tomb stands is accessible within the church. The inscription fragments are mounted at eye level on the wall above the tomb, which makes it possible to read them alongside the carved stonework below and get a clear sense of what the monument once looked like whole.