He studied canon law at Salamanca, where his brother, Pedro de Castro Lemos, who later became bishop of Cuenca (1553–1561), was named cardinal on 15 December 1583, by Gregory XIII.

He felt a great fondness for falconry, which is recorded by the "Treaty hunting Bird" by Pero López de Ayala, which is preserved at the Museum of Our Lady of Antigua, which belonged to his personal collection.

Administered, at the beginning, by the Society of Jesus, had consolidated financially the College of Jerez de la Frontera, and contributed to the maintenance of the college-seminar of the British Jesuits from Seville and since its foundation, in addition to being instituted a protector of the congregations that the company had in that city, that of the Annunciation.

About this same time, the cardinal established a party in honor of the relics that had been treasured and preserved in the museum of the convent of Santa Clara (popularly known as the Poor Clares of Monforte).

The Madrid writing school's endowment is awarded, and his nephew Pedro Fernández de Castro y Andrade would develop in his lifetime many of the features of humanism and love for the arts like his uncle.