The plot covers three decades. Father Flaherty ages from his twenties to his fifties.
To prepare for his role in this film, actor Christopher Reeve researched religion and Catholicism by visiting the Centre for Alternative Religious Broadcasting in Washington D.C., studying with a Paulist priest at a Paulist's retreat in New Jersey, and for six weeks, he did a residency at the Paulist Fathers Order's Archdiocese in New York City.
Actor Christopher Reeve blamed the film's poor box-office and critical reception on the picture's editing. Reeve also once said of this film's failure: "Monsignor should have been a good movie, and it just went off the track for reasons that I don't want to embarrass a lot of people by discussing. The way it was released, the movie is sort of a series of outrageous incidents that you find hard to believe. Since they don't have a focus, and since they aren't justified and explained, they become laughable."
When Christopher Reeve was offered this movie, Reeve was keen to play against his 'Superman' super-hero screen persona, which he had also done in Deathtrap (1982) and Somewhere in Time (1980). Reeve once commented after being cast in this film: "I thought the chance to play a morally ambiguous character who was neither clearly good nor clearly bad, someone to whom life is much more complex than the characters I've played previously would be good."
When this movie was made and released, Christopher Reeve was at the peak of his fame as a result of playing the title character in "Superman (1978)" and "Superman II (1980)," and was about to appear in "Superman III (1983)." Reeve accepted the role of Clifford Anderson in 'Deathtrap' (1982), which was released in the same year as 'Monsignor' (1982), because it had nothing to do with either Clark Kent or Superman, and he wished to avoid being typecast by his superhero persona. During the making of 'Deathtrap' (1982), Reeve said: "I've had a lot of training as an actor, and I want to use it."