He is recognized chiefly for his role in Portugal's victory in a succession war with Castile, preserving his country's independence and establishing the Aviz (or Joanine) dynasty on the Portuguese throne.

[2] John's well-remembered reign in his country earned him the epithet of Fond Memory (de Boa Memória); he was also referred to as "the Good" (o Bom), sometimes "the Great" (o Grande), and more rarely, especially in Spain, as "the Bastard" (Bastardo).

On 6 April 1385, the Council of the Kingdom (the Portuguese Cortes) met in Coimbra and declared John, then Master of Aviz, to be king of Portugal.

[6] In response to John's request, Pope Martin V issued the Papal bull Sane charissimus of 4 April 1418,[7] which confirmed to the king all of the lands he might win from the Moors.

Contemporaneous writers describe John as a man of wit who was very keen on concentrating power on himself, but at the same time possessed a benevolent and kind demeanor.

His love for knowledge and culture was passed on to his sons, who are often referred to collectively by Portuguese historians as the "illustrious generation" (Ínclita Geração): Edward, the future king, was a poet and a writer; Peter, the Duke of Coimbra, was one of the most learned princes of his time; and Prince Henry the Navigator, the duke of Viseu, invested heavily in science and the development of nautical pursuits.

In 1430, John's only surviving daughter, Isabella, married Philip the Good, Duke of Burgundy, and enjoyed an extremely refined court culture in his lands; she was the mother of Charles the Bold.