Juan Subercaseaux was born in Santiago, the son of Ramón Subercaseaux Vicuña, a career diplomat, Ambassador of Chile to the Holy See for more than two decades and Amalia Errázuriz Urmeneta, writer, author of the book "Rome of the spirit".
Young Juan was educated in the values of the faith, in a deeply Catholic family, had as spiritual director the famous Chilean priest, Miguel León Prado, who would become, years later, the first bishop of the Diocese of Linares.
After his ordination he continued his studies of Philosophy and Theology in Rome, initially at the Pontificia Università Gregoriana and, subsequently, at the Pontificio Collegio Pio Latino Americano of Rome and at the "Accademia dei Nobili Ecclesiastici" (nowadays "Pontificia Accademia Ecclesiastica)", where he obtained the doctorate in Philosophy and Theology.
Ordained Priest of Santiago de Chile on 3 April 1920, he was consecrated Bishop of Linares on 28 April 1935 by the Apostolic Nuncio in Chile, Archbishop Ettore Felici.
He was awarded the Order of the Crown of Italy and died in a road accident near La Serena.