A first St. Mary's Church was erected about 875 during the Christianization in former Carantania, led by the Bishops of Freising based at Innichen Abbey. It was first mentioned in a 894 deed as Maria Werd — as the site had then been an island, the Old High German term Wörth or Werder like Slovene Otok denotes a piece of land surrounded by water. The church served for the translation of the relics of Saints Primus and Felician and played an important role within the Christian mission in the Duchy of Carinthia. About 1150 Bishop Otto of Freising founded a college of canons here and had the small Winterkirche chapel built beside the collegiate church. In 1399 both churches were destroyed by fire and afterwards rebuilt in the present late Gothic style. The Freising Prince-Bishops gradually lost their influence in Carinthia and about 1500 the college finally became an annex of Millstatt Abbey, from 1598 led by Jesuits.
With the Suppression of the Society of Jesus in 1773, Millstatt Abbey was dissolved and Maria Wörth passed to the re-established Bendectine St. Paul's Abbey in the Lavanttal in 1809. Not until 1903 the present-day municipality was established on territory of neighbouring Schiefling and Keutschach