The old Scharnstein Castle was built around the mid-12th century by the Counts of Rebgau, who at that time had possessions in the Almtal, but also in the area on the Ager, at the Traunsee and around Vöcklabruck. After they died out, the Scharnstein dominion fell to the Babenberger, the Margraves of Austria. They gave the sovereignty as a fief to followers. In the year 1204, the name “Scharnstein” is mentioned in a deed of donation of "Heinrich von Scharnstein” for the first time. First the Pollheimers and then the Walseer followed the Babenbergers as lords of the Scharnstein dominion. In 1492, Christoph Jörger zu Reut bought the manor that he sold to the Habsburg Emperor Maximilian I in 1499. Scharnstein was owned by the Habsburgs for 85 years. However, the Habsburgs did not administer the sovereignty themselves, but gave them as a pledge. That way, Johann Fernberger who owned the Eggenberg estate, received the pledge of Scharnstein in 1534. He started with the construction of an administration building on the “Schafferleiten”, the later Scharnstein Castle, while the fortress got more and more neglected. A large part of the fortress was destroyed by a disastrous fire in 1538. "Because a chimney wasn't swept…” one commission of Inquiry found out. In 1584, Helmhart Jörger, who already ruled Pernstein, acquired Scharnstein as free property of the emperor.
During his 10-year-long reign, he established the production of scythes in Scharnstein, expanded the castle into a magnificent Renaissance building, erected a tavern and rounded off the dominion into a closed possession. Even though he was evangelical himself and admired Luther, he maintained a good relationship with Kremsmünster Abbey, its immediate neighbour. After Helmhart's death in 1594, his older son Georg inherited the reign. Years later, the younger son Karl followed him.
As a zealous Protestant, Karl became the leader of an uprising protest of the lower nobility against the emperor, but the uprising was crushed from the imperial. Karl was arrested and died in captivity at Oberhaus Fortress in Passau. His possessions were confiscated and mostly sold. In 1624 the Kremsmünster Abbey bought large parts of the lordship of Scharnstein with the castle and fortress. The Scharnstein Castle Ruins and their surroundings are still owned by the Kremsmünster Abbey today.