 At the age of ten, he became an assistant in the preparatory drawing classes at the Real Academia de Bellas Artes de San Fernando.He showed so much promise that, in 1751, the Secretary of State, José de Carvajal y Lancaster, personally provided him with the funds to go to Rome and study under the direction of Corrado Giaquinto.In 1753, when Giaquinto was called to Spain by King Ferdinand VI, Castillo returned with him and returned to the Academia, where he won a gold medal in 1756.