He took a degree in Philosophy at Santiago de Compostela University and Theology in Avila. In 1755, he ran St Clemente School and was nominated as dean of Santiago in 1774. Afterwards, he was nominated as bishop of Mondoñedo.
Andrés Aguiar published Carta pastoral del Ilmo. Sr...... dirigida a sus muy amados súbditos, así eclesiásticos como seculares (Madrid, 1802). Five years later he published another pastoral letter.
In 1785, Carlos IV made him knight of the Spanish Order of Carlos III.