That early grant is the first written evidence of a bridge here, but the place itself is older still. The name Ardfinnan derives from the Irish Ath-Arda-Fionain, meaning the Ford of Ardfinnan, which suggests that people were already crossing the Suir at this point long before anyone thought to build a permanent structure across it.

The bridge earned a grimmer kind of notice in 1399, when the Earl of Desmond drowned here, a detail recorded by later historians but unelaborated upon, leaving the exact circumstances somewhat opaque. By the mid-seventeenth century the structure was well enough established to appear by name, as the Bridge of Ardfynane, in the Civil Survey of 1654 to 1656. The bridge as it stands today runs north to south across the river and is built largely of randomly coursed limestone rubble, with cut-stone voussoirs, the wedge-shaped blocks that form the curved arch-rings, framing each of its nine semi-circular spans. Eight triangular cut-waters project from the eastern face, angled to deflect the current and reduce pressure on the piers, and three overflows are incorporated into the structure. The parapet, just over a metre high, is capped with large flat capstones for most of its length, though the south-eastern end has seen these replaced with concrete, as have the rendered arch soffits beneath the spans, small concessions to maintenance that sit alongside the older stonework without quite matching it.