It is believed that there was an earlier (Pre-Reformation Catholic) church on the site dedicated to local saint Ibar of Beggerin. The current building is believed to date from some time after the Restoration of King Charles II in 1660.[7] In 1690, the Rector of St Iberius, Alexander Allen, accused then Mayor of Wexford, Edward Wiseman, of inciting vandals to demolish the altar and pews and steal vestments and books. St. Iberius' was rebuilt in 1760–66 to a Georgian style. A cast iron bell in the church is dated "1816."[8]
The church is built to a cruciform plan and is wider than it is long (supposedly to fit next to the old town walls), with an upper gallery which was used originally to seat Wexford's large population of soldiers.[9][10] The building was refronted some time around 1882, producing the present facade. The organ was installed in 1893. In 1930, a prayer desk was added in memory of Dr Thomas Dowse.[8]
St Iberius is known for its excellent acoustics and is commonly used for concerts.[12][5] In 1996 a Russian pianist won a Kawaigrand piano in a competition, but rather than bring the piano back home, he sold it to St Iberius'.[8]