The Duchy of Cadaval was created by King John IV on April 26, 1648, the day of birth of Prince Dom Pedro, future Dom Pedro II, king of Portugal. The title was created in favor of Dom Nuno Alvares Pereira de Melo (1638-1727), son of Don Francisco de Melo, one of the mainstays of Restoration of Independence in 1640, who would inherit the titles of Earl of Tentúgal and Marquess of Ferreira.

Thanks to the fusion of these houses, Dom Nuno became the most powerful noble of the kingdom, which contributed greatly to this family fight in the cause of independence, both during the succession crisis of 1580, as the Restoration of Independence in 1640.

Among the privileges of the House of Cadaval, they had the Master's power authority to appoint or confirm the local town councils, and may appoint the ombudsmen, clerks, investigators, accountants and other positions in the lands under their jurisdiction.

So far, the Duchy of Cadaval had 11 Dukes. The current Duchess of Cadaval is Dona Diana Alvares Pereira de Melo, 11th Duchess of Cadaval, title confirmed by Dom Duarte Pio, Duke of Braganza, Head of the Royal House of Portugal.

On June 21, 2008, Dona Diana Alvares Pereira de Melo, 11th Duchess of Cadaval, has married HRH the Prince Charles-Philippe d'Orleans, Duke of Anjou.