In 1819 he became Cardinal Protoprete (Protopriest) and consequently opted for the titulus of San Lorenzo in Lucina, that two centuries earlier had belonged to his forebear and namesake Giulio Gabrielli the Elder (1604–1677). In 1820 he resigned from Prefect of the Congregation of the Council and was appointed Pro-Datary of His Holiness.
He assumed the cardinalate in 1819 and subsequently claimed the San Lorenzo in Lucina title, a position his ancestor Giulio Gabrielli the Elder had held two centuries earlier. Two years later, he relinquished his role as Prefect of the Congregation of the Council and was appointed Pro-Datary to the Holy See.