[3] After finishing his philosophy coursework in 1769, he began studying theology at San Clemente al Laterano, a convent for seminarians run by the Irish Dominicans.

[4] Concanen was ordained a priest in the Dominican Order by Patriarch François Mattei on December 22, 1770, at the Archbasilica of Saint John Lateran in Rome.

In a letter to a friend, he explained:Conscious of my inability for the awful Episcopal Charge, I have, from the very beginning, renounced my appointment...I am resolved to live and die in the obscure and retired way of life I have chosen from my youth.

[3]In 1798, a French army under General Louis-Alexandre Berthier entered Rome, sent Pius VI into exile and ravaged both San Clemente and the Dominican House of Studies.

[7] On April 8, 1808, Concanen was appointed the first bishop of the newly erected Diocese of New York by Pope Pius VII.

Concanen received his episcopal consecration in Rome on April 24, 1808, from Cardinal Michele di Pietro, with Archbishops Tommaso Arezzo and Benedetto Sinibaldi serving as co-consecrators.

[5] [8] Soon after his consecration, Concanen attempted to sail from Livorno, Italy, on an American ship to New York City.

However, since that ship had also visited the United Kingdom, then at war with France, French authorities in Tuscany had stopped it from leaving port.

However, soon after arriving there, the Kingdom authorities, allied with the French, denied him permission to board the ship because he was an Irish national.

[11][8] On July 9, 1978, Cardinal Terence Cooke of New York, accompanied by Auxiliary Bishops Anthony F. Mestice and Patrick V. Ahern, traveled to Naples to attach a commemorative plaque to Concanen's tomb in the church.