Barnabò was born on 2 March 1801 in Foligno.
He joined the priesthood and was ordained in March 1833. Between his ordination and 1856 he held a number of official positions including Privy chamberlain supernumerary, Consultor to the Propaganda Fide, Keeper of the Seals of the Apostolic Penitentiary and served as a domestic prelate to the Pope.
Barnabò was elevated to cardinal on 16 June 1856 and was appointed Cardinal Priest of Santa Susanna, a position he held until his death.
Between 1856 and 1874, Barnabò served as the Prefect of the Congregation Propaganda Fide. Some records suggest Barnabò's administered the Congregation with almost totalitarian gusto and "controlled the missions like an empire" and ran the Congregation itself "like a dictator".
As Prefect, Barnabò was responsible for arranging a meeting between Pope Pius IX and Isaac Hecker. Hecker had been expelled from his Redemptorist order but Barnabò recognised his valuable missionary work and helped him appeal to the Pope who overturned the expulsion.
For a year (1868–1869), as was customary for the office, Barnabò was appointed Camerlengo of the Sacred College of Cardinals. He succeeded friend and fellow papal power-broker, Cardinal Karl-August von Reisach.
He participated in the First Vatican Council between 1869 and 1870.
Barnabò died on 24 February 1874.
- Rome in Australia: The Papacy and Conflict in the Australian Catholic Missions - C. Dowd OP (reprint: 2008)
- S. Miranda: Alessandro Barnabò
- A History of the Popes, 1830-1914 - Chadwick (2000, Clarendon/Oxford University Press)
- Acton and History - Chadwick (2002)
- Catholic Australia: Mary MacKillop
|Catholic Church titles|
|Cardinal Priest of Santa Suzanna
1856 – 1874
Giacomo Filippo Fransoni
|Prefect of the Congregation Propaganda Fide
1856 – 1874
Karl-August von Reisach
|Camerlengo of the Sacred College of Cardinals
1868 – 1869
Giuseppe Milesi Pironi Ferretti