The film Black Robe is based upon the novel (New York: Dutton, 1985) of the same name by the late Canadian author Brian Moore. He also composed the screenplay, making some minor changes in the process. For instance, Fr. Laforgue is nearly deaf during much of the novel's narrative (a metaphor for his failure to understand the natives' culture, some critics suggest), whereas he has no such handicap in the film. Also, in the film the character Chomina is both chief and father to Annuka; in this instance Moore has merged his novel characters of Chief Neehatin and Chomina into one. In the novel, the Algonquins use more vulgar language in unusual places, (with one urging Daniel to "Eat, fucking eat") and the Iroquois are far more violent. For the most part, however, Moore's screenplay remains true to his novel about a young Jesuit priest whose faith is challenged by his experiences in a foreign land.
Moore claims that his source material for the novel comes from Graham Greene's Collected Essays, one of which discusses American historian Francis Parkman's book The Jesuits in North America. Not known prior to the novel Black Robe for being an historical novelist, Moore breaks with his own tradition and writes this story using historical documents as sources. He consults not only Parkman's account but also the historian's source, The Jesuit Relations, a 73-volume account of that religious order's missionary work in North America during the 17th and 18th centuries. In particular, the film and novel's narrative is taken from an account of Fr. Paul LeJeune's 1634 trip to the Huron mission. Moore also claims to have done research into the history and customs of the Iroquois, Algonquin, and Huron peoples and lists various people and places he consulted in the introduction to his novel.