- A retired Belgian police officer. Poirot is Christie's most famous detective and is known for his short stature and long, curly moustache. Poirot is very intelligent, extremely aware and instinctual and is a brilliant detective. The novel is generally written from his perspective.
in-depth analysis of Hercule Poirot.
- The director of the Compagnie Wagon Lits and formerly worked for the Belgian police force with Poirot. Traveling on the Orient Express, M. Bouc asks Poirot to take the case. M. Bouc provides comic relief in the novel, constantly frustrated with the case and confused by Poirot.
- The coroner aboard the Orient Express. Dr. Constantine is often Poirot or M. Bouc's sidekick and is present for most of the evidence gathering. Dr. Constantine examines Ratchett's body and determines when he could have been killed.
- Daisy Armstrong's governess. Mary Debenham is a calm, cool and unruffled lady, instrumental in the planning of Ratchett's murder. Poirot is most suspicious of Mary because of conversation he overhears between herself and Colonel Arbuthnot on the train to Stamboul.
in-depth analysis of Mary Debenham.
- Really Linda Arden, famous actress and grandmother of Daisy Armstrong. Mrs. Hubbard provides constant interruption and diversion on the train and is known for her stories about her daughter. Mrs. Hubbard's compartment is next to Ratchett's.
in-depth analysis of Mrs. Hubbard.
- A friend of Colonel Armstrong, and father of Daisy Armstrong. Like Mary Debenham, Poirot suspects him because he called Mary by her first name on the train to Stamboul. Colonel Arbuthnot is hard-willed, polite and very "English."
- A Russian princess. Princess Dragomiroff is a generally despicable, ugly old lady; her yellow, toad-like face puts off Poirot. She is the owner of the famous "H" handkerchief found in Ratchett's room and tells Poirot many lies about the other passenger's identities.
- Ratchett's personal secretary. Hector is truly in cahoots with the Armstrong family. McQueen tries to hard to tell Poirot that Ratchett did not speak any French—making him an immediate suspect in the case.
- Real name Cassetti, kidnapped and murdered the young Daisy Armstrong for money. The Armstrong family murders Ratchett because he escaped punishment in the U.S. Poirot describes Ratchett as a wild animal.
- The sister of Sonia Armstrong, did not murder Ratchett. Because the Countess is closest to the Armstrong case, she attempts to conceal her identity by dropping grease on her passport and smudging the name label on her luggage. The Countess is quite young, dark haired and beautiful.
- A very defensive man who tries to conceal the true identity of his wife, Countess Andrenyi. The Count takes his wife's place in the murder.
- The big flamboyant American. Cyrus is a detective with a well-known detective service in New York City. He becomes involved with the Armstrongs because he was in love with Daisy's French nurse who committed suicide after Daisy was killed. Cyrus pretends to help Poirot with the case.
- M. Bouc is sure that Antonio, a big menacing Italian man, had something to do with the murders, primarily because M. Bouc distrusts Italians. Revealed by Poirot, Antonio was the Armstrong's chauffer. Antonio loved dear little Daisy and tears when he speaks of her.
- Greta Ohlsson weeps and weeps and weeps. The Swedish lady was Daisy Armstrong's nurse and is a very delicate type—not meant for murder.
- Has a kindly face set in an expression of "placid stupidity." Hildegarde is rather slow-minded and unquestioningly carries out the ugly Princess's orders. Hildegarde pretends to be Princess Dragomiroff's maid, but is truly the Armstrong's cook.
Edward Henry Masterman
- Ratchett's valet, brought into the murder plot by Hardman. Masterman is not a terribly colorful character, mainly referred to by his function—"the valet." Masterman is very polite and obedient, perhaps even haughty.
- Father of the suicidal nursemaid of Daisy Armstrong, is the Conductor of the Orient Express. Pierre, like the other servants does not initially receive much scrutiny—he is not a top suspect. However, as the novel progresses, his involvement in the murder is proven essential.