He was named, by Cardinal Antonio Barberini (brother of then-Pope Urban VIII), superintendent of the abbey of Farfa and custodian of the Vatican Library in 1630.
[1] In 1627, the Congregation of Propaganda Fide proposed sending Giustiniani to Ancona for secret talks with Cyril Lucaris, patriarch of the Eastern Orthodox Church.
[4] Pope Urban VIII was not convinced and instead entrusted the decision to a panel of advisors including his brother (and Giustiniani mentor), Antonio Barberini.
There are reports Patelerio hurt his own chances by later going into Rome and blessing the people with a cross raised above his head; actions that created confusion and concern among the citizenry.
Four years later, Pamphili was elected to the Papal Throne as Pope Innocent X and Giustiniani was elevated to Cardinal on 6 March 1645.