In the wake of Pope Francis's death on April 21, 2025, numerous sources have cited this film for its accuracy in detailing the conclave process. When the pope is found deceased, he is asked three times if he is dead before the "sede vacante" is declared. The papal ring (called the Ring of the Fisherman) is removed and destroyed, to prevent it from being used to forge the pope's seal on documents. An official announcement that the throne of the Holy See (the Catholic church's governing body) is vacant is made, which begins a nine day period of mourning. The papal apartment is closed off with crimson ribbon and sealed with a wax papal stamp. The College of Cardinals are sequestered in apartments (Domus Sanctae Marthae, or Saint Martha's House) to eat and sleep between votes. Finally, the windows and doors to the Sistine Chapel, where the actual election takes place and ballots are cast, are darkened, shuttered, and locked to maintain the secrecy of the conclave. Newer security measures are shown as well, such as the Sistine Chapel being swept for electronic listening devices. ID cards are issued to all conclave servants after a reporter disguised as a servant was discovered during the conclave that elected Pope Benedict XVI in 2005. All members of the College of Cardinals are required to surrender their mobile phones and other electronic devices, Vatican City's Wi-Fi network is temporarily shut down, and wireless signal jammers are activated within the Sistine Chapel itself.
Costume designer Lisy Christl was unimpressed with the red robes that cardinals currently sport, deeming them to be too drab. She chose a red used in 17th century vestments as they were much more vibrant.
In 533, John II became the first pope to adopt a papal name. He thought his birth name, Mercury, was inappropriate because it was also the name of a Roman god. The last pope to keep his own name as a papal name was Marcellus II, in 1555.
When Lawrence looks in the deceased Pope's bedside drawer, there is a bunch of rubber bands. This is another hint that the deceased Pope was Pope Francis, because it was reported that on his elevation to Pope, he called his Buenos Aires newsagent personally to let him know he wouldn't be continuing his custom of returning the rubber bands from his daily newspaper at the end of each month.
While writing the screenplay, Peter Straughan said that he met with a cardinal to discuss the logistics of the conclave. He also took a private tour of the Vatican, and said he did not feel hostility while there and felt that the Vatican had been open to him.