[1] He was born in Isny im Allgäu in the Kingdom of Württemberg,[2] the son of Franz Ehrle, a physician, and Berta von Frölich; he was educated at the Jesuit school Stella Matutina in Feldkirch.

For the regency phase of his training in the Jesuit order from 1868-1873, Ehrle was sent to teach at his old secondary school, Stella Matutina, where he taught English, French and philosophy.

After being ordained a priest on 24 September 1876 in Liverpool,[3] Ehrle carried out pastoral work in a home for the poor at Preston, Lancashire, before being transferred in 1878 to Tervuren, Belgium, where the German Jesuit periodical Stimmen aus Maria-Laach (Voices from Maria Laach) had established its office in exile, to serve as its editor.

When Pope Leo XIII opened the Vatican Secret Archives in 1880, Ehrle was called to Rome to do research on the official correspondence between the Holy See and Germany during the Thirty Years War.

Ehrle became more and more involved, but, responding to Pope Leo's call for a renewal in Thomistic studies, his interests shifted to gathering and cataloging books and manuscripts relating to scholasticism, and he visited other European libraries to do so.

Nothing similar took place again until the 1930s when the international museum committee of the League of Nations organized conservation conferences in Rome, Paris and Athens.

He was promoted to the office of Cardinal Deacon by Pope Pius XI at the papal consistory of 11 December 1922, and given the titular church of San Cesareo in Palatio.