The unnamed narrator is an expatriate living in Paris who serves as a loyal, observant companion to his highly analytical friend. Recognizing his own intellectual limitations compared to his companion, he acts as an attentive listener and a sounding board. He happily resides in a time-eaten and grotesque mansion in Faubourg St. Germain, captivated by the process of deductive reasoning and documenting their unusual shared experiences.

Monsieur C. Auguste Dupin is an eccentric, highly observant man from an illustrious family who has fallen into financial hardship. Content to live a secluded life surrounded by books, he possesses a startlingly sharp analytical mind that allows him to deduce the thoughts and actions of others with seemingly supernatural accuracy. He views human behavior and mysteries as puzzles to be solved through strict, empirical logic, preferring the isolation of the night to daytime society.

Madame L'Espanaye is an elderly former landlady who lives an exceedingly private life in a fourth-story apartment. Presumed by a local laundress to be a fortune-teller, she ventures out infrequently and maintains a strictly guarded daily routine. Shortly before the main investigation begins, she notably withdraws a large sum of 4,000 gold francs from her bank.

Mademoiselle Camille L'Espanaye is the adult daughter of Madame L'Espanaye, sharing a secluded fourth-story apartment on the Rue Morgue. She relies on her mother and is rarely seen taking independent action, leading a quiet existence isolated from the bustling Parisian society around them. She occasionally assists with practical matters, such as accepting bags of money from a bank clerk through a partially opened doorway.

The Sailor is a stout, muscular, and sunburnt traveler with an unrefined demeanor whose hair covers a large portion of his face. He carries an oaken cudgel and displays an uneasy conscience regarding his recent activities. Though rough in physical appearance and lacking formal social graces, he possesses a functional moral compass when pressed for honesty.

The Ourang-Outang is a large mammal originally captured in Borneo by a traveling sailor. Kept strictly confined to ensure submission, the creature reacts to its environment based entirely on animal instinct rather than human logic. It demonstrates a startling ability to mimic human behaviors when left to its own devices.

G– is the chief of the Paris police, a man known for his by-the-book methodology and conventional administrative skills. While diligent and active in his physical duties, he lacks the profound imagination necessary for complex analytical reasoning. Consequently, he favors routine procedures over creative deduction and resents outside interference.

Adolphe Le Bon is a clerk at a local Parisian bank who assists Madame L'Espanaye with a massive withdrawal of 4,000 gold francs. He physically escorts the funds to her apartment, making him one of the few individuals to interact directly with the reclusive women shortly before a major police investigation begins.