Father Diéguez was born in Orense, Spain in 1961. He finished his university studies in Business Administration and holds a doctorate in Sacred Theology. He was ordained priest in 1990.
In 1997 to 2011 he was the Spiritual Director of the Roman College of Holy Mary, an international center of Opus Dei in Rome for the formation of young women from around the world. In 2011 to 2017 he was the Rector of the Sedes Sapientiae international seminary in Rome.
In 2017 he served as the Vice Rector of the Roman College of the Holy Cross, an international seminary of the prelature of Opus Dei, and subsequently as its Rector in 2018 to 2022.
He authored a book on spiritual formation entitled He Knows Not How: Growing in Freedom. The book aims to help people live their Christian life with true freedom, by strengthening their understanding and reflection on matters of faith and morals. It has been published in Spanish, English, French, Portuguese, Italian and German.
Father Diéguez was in the Philippines in 2004 and 2012.