After taking over, his son Johann Wilhelm von Hardegg set about buying up indebted estates and thereby got himself into a serious financial crisis.
A few days later, the buyer set off for Riegersburg with his son Johann Joseph von Khevenhüller-Metsch, who had co-signed the purchase contract, where he found a dilapidated and most likely uninhabitable building.
The castle in its current form was built in several phases between 1730 and 1780 according to plans by Franz Anton Pilgram, a student of Johann Lucas von Hildebrandt.
In 1945, some displaced persons from neighboring South Moravia were housed in the castle, then the Soviet occupying forces moved in.
The castle was partially renovated for the Lower Austrian State Exhibition in 1993 under the motto "Family – Ideal and Reality".