The costume designer Lisy Christl, who designed the costumes for All Quiet on the Western Front, returned to work with Edward Berger on Conclave. They began developing ideas for the wardrobe about a year before filming began.
Her costumes were multi-layered and richly decorated, and she managed to individualize the religious robes worn at a Conclave with cardinals from all over the world.

Conclave (2024) Ralph Fiennes
She had a passionate interest in this film for many reasons! Christl said:
“It opens a door into the world of the Vatican. And that’s a world that interests me profoundly. In general, clothing related to religion is my field. For me it was truly a dream come true.
I think whether you are a believer or not, it is a very mystical and complex world. To spend so much time in Italy after extensive research was a gift. And now, after five months in Rome I see the roman catholic world with different eyes, I think after this film you really know more. I loved working in Italy; my Italian, German, Greek and Austrian costume crew are true artists.

Conclave (2024) Ralph Fiennes and Stanley Tucci
Christl did extensive research on the history, with the help of Francesco Bonomo (liturgical consultant) to create something that mirrors the vestments worn today, but the fabric and color are different. The colors are so much deeper, so much richer, so much more powerful, so much stronger. Her work is detailed, ornate and tactile.
As mentioned earlier, Christl had to distinguish the cardinals, who all wore the same robe, from one another, which was not unlike her task in “All Quiet on the Western Front”. This time, she managed to do so through details such as the crosses, rings (by Riccardo Penko from Florence), shoes and cloaks the cardinals wear. For example, Tedesco (the patriarch of Venice), a conservative cardinal who believes in the pre-Vatican II era, contrasts with Lawrence, the modest man who prefers to stay in the background, through his luxurious accessories.

Conclave (2024) Jonathan Lithgow
This led to a happy accident:
“There was a misunderstanding with the tailor about Cardinal Bellini’s coat,” she recalls. ‘He thought it was supposed to be a cassock, but it was supposed to be a coat. When I saw it, I thought that yes, everything happens for a reason, and when Stanley tried it on, it all made sense and he represents Bellini as a modern cleric.