From 1906 the castle was rented to American businessman (and in 1912 Titanic survivor) Thomas Cardeza, a grandson of the founder of Fidelity Trust Company in Philadelphia, and his French-born wife Mary (née Racine and descendant of Jean Racine), both of whom had lived between 1903 and 1906 in nearby Nitrianska Streda. The Cardezas also made transformations, including building the southern wing's second floor, and kept a small zoo including bears and monkeys in the castle's garden. They left Kovarce after the American entry into World War I in April 1917, but kept renting the property until 1920.
From 1906 to 1920, the castle was leased by Thomas Cardeza, a grandson of the founder of Fidelity Trust Company in Philadelphia and his wife Mary (née Racine), who were both residents of Nitrianska Streda before moving to Kovarce. The Cardezas made renovations, including adding a second floor to the southern wing, and kept a small zoo with bears and monkeys in the castle's grounds. They left Kovarce after the United States entered World War I in 1917 but continued renting the property until 1920.