His father served from 1801 until his death as the commander for the Papal Noble Guard after Pope Pius VII named him to that position.

His rise through the ranks continued after he was appointed as the Titular Archbishop of Ephesus; he received his episcopal consecration from the pope himself in Saint Peter's Basilica.

His name was not announced until 21 April 1845 and he was made the Cardinal-Priest of Santa Maria in Campitelli (the diaconate was elevated pro hac vice to a titular rank).

Altieri was a member of the Red Triumvirate that governed Rome between 1849 and 1850 after the short-lived Roman Republic together with cardinals Luigi Vannicelli Casoni and Gabriele Sermattei della Genga.

He was the aide for the Congregation for Memorials from 1855 to 1857 and was later appointed Camerlengo of the Holy Roman Church on 19 March 1857; the cardinal held that position until his death.

[1] The beatification process commenced under Pope Benedict XVI once the Congregation for the Causes of Saints issued the nihil obstat ("no objections") and titled him as a Servant of God on 14 March 2009.