In 1817, Johann Baptist von Streng sold it to the exiled Hortense de Beauharnais, the daughter of ex-Empress Joséphine, for 30,000 guilders.
As arranged by Napoleon, Hortense had to marry his brother Louis Bonaparte, and the couple were named King and Queen of Holland (1806–10).
Her brother, Eugène de Beauharnais, bought the nearby Schloss Sandegg and built a villa close by.
In 1837, while he was exiled and living in New York City, Louis Napoleon received notice of his mother's deteriorating health and returned to Arenenberg.
After Napoleon III's death, Eugénie visited Arenenberg several times before she donated it in 1906 to the Canton Thurgau.