Meg Tilly said that her best film experience was working with director Norman Jewison and actresses Jane Fonda and Anne Bancroft on this picture.
Anne Bancroft said of the film's larger questions: "After seeing 'Agnes of God' I would like people who believe in God to think again and people who don't believe in God to think again, as well."
The role of the Mother Superior, Mother Miriam Ruth, was originated on Broadway by Geraldine Page; Page was passed over for the film version in favor of Anne Bancroft. Bancroft was Academy Award nominated for Best Actress in a Leading Role for this movie but, ironically, lost the Oscar to Page in O Regresso para Bountiful (1985).
Despite the fact that her character is a chain-smoker, Jane Fonda had quit smoking ten years before she made this movie. For the role, she smoked reed cigarettes - non-toxic, tobacco-free cigarettes made from cattail reeds, which are sold in health stores to people who are trying to quit smoking.
"You can't just start shooting a picture without knowing anything about that kind of life," said the film's cinematographer Sven Nykvist, "even though I know much of it because my father was a minister. Part of our-preparation for filming 'Agnes' was attending vespers. It was silent. They prayed and sang, and I felt very, very much in harmony when I was sitting there looking at everything. I forgot very quickly that I was just there to study," he said.