Around the middle of the 13th century, the Lords of Werd-Capellen lived here in a relatively modestly sized castle. Due to the involvement of the castle lords in the Kuenringer noble revolt against Duke Albrecht I, the Mollenburg was destroyed, but was soon rebuilt. The castle was first mentioned in a document in 1303.
In 1307 the rule went to a Lord von Streitwiesen. In 1486 it was sold by the Ebersdorfers to Kaspar von Rogendorf, the owner of the Pöggstall estate. He expanded the castle. In the 16th century the princely fief became his own property. However, after the escape of the bankrupt Christoph Freiherr von Rogendorf, it was confiscated in 1546. As a result, the Geyers of Osterburg partially converted the castle into a Renaissance castle. After various changes of ownership, the rule passed to Emperor Ferdinand I in 1839. After renovation in 1844, the Mollenburg was reduced to ruin in 1860 by the administrator Johann Niedermayer for tax reasons (roof tax). The roof structure was removed, devastated and the usable parts were sold. In 1920 the Habsburg property became part of the war victims' fund.
Confiscated by the Soviets in 1945, the Mollenburg was transferred to the administration of the Austrian Federal Forests in 1956. The art historian, novelist and politician Jörg Mauthe acquired the ruins for 220,000 schillings in 1972 and restored them, partly by himself and with the help of his sons. Individual buildings in the outer bailey were made habitable again.
The Mollenburg is still privately owned by the Mauthe family today; Jörg Mauthe's urn is kept in the tower of the old castle.