[3] In 1417, Juan began his studies at the Colegio Mayor de San Bartolomé at the University of Salamanca.

After obtaining his doctorate, Juan de Mella became a professor of canon law at the University of Salamanca.

[8] During the pontificate of Pope Martin V, he traveled to Rome as Procurator of King John II to defend Archbishop Diego de Anaya before the papal court.

[9] At the end of 1432, Pope Eugene appointed Mella Auditor of the Roman Rota; he took his oath of office on 23 January 1433.

[17] Mella was transferred to the see of Zamora on April 6, 1440, while his brother Fernando became auxiliary bishop and vicar general of León in his place.

[2] In Zamora Cathedral Mella endowed the chapel of San Ildefonso (now known as the capilla del cardenal after him) with five chaplaincies and an altar by Fernando Gallego.

[18] In 1455, Bishop de Mella was in Wrocław, where he conducted a court case involving the Grand Master of the Teutonic Knights and his subjects, and found for the former.

[20] In March 1465 he was transferred to the title of San Lorenzo in Damaso[21] Cardinal Mella participated in the papal conclave of 1458 that elected Pope Pius II.

[2] He was buried in San Giacomo degli Spagnoli, a church on the Piazza Navona that was replaced in the nineteenth century by Nostra Signora del Sacro Cuore because of its ruined condition.