Cardinal Monteiro de Castro was born March 29, 1938 in S. Eufemia, Portugal.

He was ordained a Priest on July 9, 1961 for Braga, Portugal. On February 16, 1985, he was appointed Titular Archbishop of Beneventum,  Apostolic Pro-Nuncio to Bahamas, Barbados, Belize, Dominica, Grenada, Jamaica, Saint Lucia, Trinidad and Tobago, Antilles.

On March 23, 1985 he was ordained Bishop.

On April 25, 1987 he was appointed Apostolic Pro-Nuncio to Antigua and Barbuda, Antilles, and in 1990 was appointed Apostolic Nuncio to both El Salvador and Honduras, resigning from the latter in 1991.

On February 2, 1998 he was appointed Apostolic Nuncio to South Africa, Namibia, Swaziland, and Lesotho. On March 1, 2000 he was appointed Apostolic Nuncio to Spain and Andorra.

On July 3, 2009 he was appointed Secretary of the Congregation for Bishops, and on October 21 of that year was appointed Secretary of the College of Cardinals.

On January 5, 2012 he was appointed Major Penitentiary of the Apostolic Penitentiary.

He was appointed Cardinal-Deacon of San Domenico di Guzman on February 18, 2012, and elevated to Cardinal. He was installed April 22, 2012.