Entering the Congregation of the Missionary Sons of the Immaculate Heart of Mary in 1899, Larraona Saralegui received his habit on 28 July 1902, and professed his final vows on 8 December 1903.

Within the Claretians, he held the posts of counselor of the Italian province, visitor to Germany, and general assistant to Italy, Central Europe, and China.

He thus became the first Claretian member of the College of Cardinals; he required the permission of his order to change his brown habit for scarlet robes, provided they were made of wool.

Attending all four sessions of the Second Vatican Council, he served as a cardinal elector in the 1963 papal conclave that selected Pope Paul VI.

He resigned as prefect of rites on 9 January 1968, and later exercised his right as a cardinal-deacon of ten years' standing to become a cardinal-priest (receiving the title of S. Cuore di Maria in the consistory of 28 April 1969).