The Romans built a fort or naval base in Pöchlarn as early as 174. The legendary Harlungoburg was probably built in its ruins in the 8th century. In 832, King Louis the German gave the surrounding area to Bishop Baturich of Regensburg. Margrave Rüdiger resided here around 950.
Afterwards, Pöchlarn was the seat of the new Margraviate of Austria under the first Babenberg Leopold I. After the Babenbergs moved their residence to Melk in 984, the diocese of Regensburg took over the existing buildings and set up an official residence for the carers it had appointed. Under Bishop Gebhard IV, the Pflegerhof was moved to the former farm yard on the eastern city wall.
A permanent house was built as a new residence, which was protected by a moat and a kennel. This was first referred to as the bishop's court in 1334. The first carers known by name were Chuno von Perkham (1130) and Christian von Harlungen (1156). Financial problems repeatedly forced the diocese to mortgage Pöchlarn. In 1391 it was even sold to the people of Wallse, but it was bought back by the bishops in 1413. In 1576, Bishop David Kölderer had the permanent house expanded into a Renaissance moated castle by his caretaker Oswald von Fränkhing. It remained the property of the diocese of Regensburg until 1801, served as an administrative center and was looked after by employed nurses.
Through the Peace of Luneville, the entire property of the diocese came to the Elector and Archbishop of Mainz Karl Theodor. Emperor Franz II had the estate confiscated in 1810 and initially administered by the Imperial Court Chamber. In 1823 it was sold at public auction. Friedrich Ritter von Bors and Borod was awarded the contract. He had an extension in the north of the old castle torn down and the so-called new castle built in its place. In 1900 the building came to the Barons of Tinti, who owned it until 1985. The last private owner of the castle was Maria Amberger. The city of Pöchlarn then took over the castle. In 2002, the “Schloss Pöchlarn Nursing Home Betriebs- und Verwaltungs GesmbH” acquired the building. She had it extensively restored and modernized.
Since then, the castle has served as a retirement home and nursing home.