His uncle also issued a decree, on 19 May 1750, placing João in the order of precedence lower than the Portuguese Royal Family, but above all other nobles.
He served as a counselor of state and mordomo-mor (chamberlain of the royal household) for both his uncle King João V and his cousin Queen Maria I.
He also served as Captain-General of the Royal Armada, the highest-ranking official of the Portuguese Navy, during the reign of Queen Maria.
João married Maria Margarida de Lorena, 2nd Duchess of Abrantes, on 20 February 1757.
As the couple did not produce children, his wife's titles were inherited by her cousin, D. Pedro de Lancastre.