The play's cast consisted of 16 speaking parts and several extras; the film script enlarged it to 22 speaking parts and hundreds of extras. The cast is notably international: only three of the credited actors were born in the United States. The top-billed actors are:
- Humphrey Bogart as Rick Blaine. Rick was his first truly romantic role.
- Ingrid Bergman as Ilsa Lund. Bergman's official website calls Ilsa her "most famous and enduring role". The Swedish actress's Hollywood debut in Intermezzo had been well received, but her subsequent films were not major successes until Casablanca. Film critic Roger Ebert called her "luminous", and commented on the chemistry between her and Bogart: "she paints his face with her eyes". Other actresses considered for the role of Ilsa included Ann Sheridan, Hedy Lamarr, Luise Rainer and Michèle Morgan. Wallis obtained the services of Bergman, who was contracted to David O. Selznick, by lending Olivia de Havilland in exchange.
- Paul Henreid as Victor Laszlo. Henreid, an Austrian actor who had emigrated in 1935, was reluctant to take the role (it "set [him] as a stiff forever", according to Pauline Kael), until he was promised top billing along with Bogart and Bergman. Henreid did not get on well with his fellow actors; he considered Bogart "a mediocre actor." Bergman called Henreid a "prima donna".
The second-billed actors are:
- Claude Rains as Captain Louis Renault. Rains was an English actor born in London. He had previously worked with Michael Curtiz on The Adventures of Robin Hood. He later played the villain in Alfred Hitchcock's Notorious, reteaming with Ingrid Bergman.
- Conrad Veidt as Major Heinrich Strasser. He was a German actor who had appeared in The Cabinet of Dr. Caligari. He fled the Nazis, but was frequently cast as a Nazi in American films.
- Sydney Greenstreet as Signor Ferrari, a rival nightclub owner. Another Englishman, Greenstreet had previously starred with Lorre and Bogart in his film debut in The Maltese Falcon.
- Peter Lorre as Signor Ugarte. Born in Austria-Hungary, Lorre had left Germany in 1933 after starring in Fritz Lang's first sound movie, M (1931). Greenstreet and Lorre appeared in several films together over the next few years, although they did not share a scene in Casablanca.
Also credited are:
- Curt Bois as the pickpocket. Bois was a German-Jewish actor and refugee. He had one of the longest careers in film, making his first appearance in 1907 and his last in 1987.
- Leonid Kinskey as Sascha, the Russian bartender infatuated with Yvonne. He was born into a Jewish family in Russia and had immigrated to the United States. He told Aljean Harmetz, author of Round Up the Usual Suspects: The Making of Casablanca, that he was cast because he was Bogart's drinking buddy. He was not the first choice for the role; he replaced Leo Mostovoy, who was deemed not funny enough.
- Madeleine LeBeau as Yvonne, Rick's soon-discarded girlfriend. The French actress was married to Marcel Dalio until their divorce in 1942.
- Joy Page as Annina Brandel, the young Bulgarian refugee. The third credited American, she was the stepdaughter of Jack L. Warner, the studio head.
- John Qualen as Berger, Laszlo's Resistance contact. He was born in Canada, but grew up in America. He appeared in many of John Ford's films.
- S. Z. Sakall (credited as S. K. Sakall) as Carl, the waiter. He was a Jewish-Hungarian actor who fled Germany in 1939. His three sisters later died in a concentration camp.
- Dooley Wilson as Sam. He was one of the few American members of the cast. A drummer, he had to fake playing the piano. Even after shooting had been completed, Wallis considered dubbing over Wilson's voice for the songs. Producer Wallis considered changing the character to a woman and thought of casting singers Hazel Scott or Ella Fitzgerald.
Notable uncredited actors are:
- Leon Belasco as a dealer in Rick's Cafe. A Russian-American character actor, he appeared in 13 films the year Casablanca was released.
- Marcel Dalio as Emil the croupier. He had been a star in French cinema, appearing in Jean Renoir's La Grande Illusion and La Regle de Jeu. After he fled the fall of France and went to America, he was reduced to bit parts in Hollywood. He had a key role in another of Bogart's films, To Have and Have Not.
- Helmut Dantine as Jan Brandel, the Bulgarian roulette player married to Annina Brandel. Another Austrian, he had spent time in a concentration camp after the Anschluss, but left Europe after being freed.
- William Edmunds as a contact man at Rick's. He usually played characters with heavy accents, such as Martini in It's a Wonderful Life (1946).
- Gregory Gaye as the German banker who is refused entry to the casino by Rick. Gaye was a Russian-born actor who went to the United States in 1917 after the Russian Revolution.
- Torben Meyer as the Dutch banker who runs "the second largest banking house in Amsterdam". Meyer was a Danish actor.
- George London, one of those who sing "La Marseillaise". London was a Montreal-born bass-baritone opera singer.
- Georges Renavent as a conspirator.
- Corinna Mura as the guitar player who sings "Tango Delle Rose" while Laszlo is consulting with Berger, and later accompanies the crowd on "La Marseillaise".
- Dan Seymour as Abdul the doorman. He was an American actor who often played villains, including the principal one in To Have and Have Not, and one of the secondary ones in Key Largo, both opposite Bogart.
- Gerald Oliver Smith as the Englishman whose wallet is stolen. Smith was an English actor who appeared in National Velvet (1944), That Forsyte Woman (1949) and One Hundred Men and a Girl (1937).
- Norma Varden as the Englishwoman whose husband has his wallet stolen. She was a famous English character actress.
- Jean Del Val as the French police radio announcer who (following the opening montage sequence) reports the news of the murder of the two German couriers.
- Leo White as the waiter Emile (not to be confused with the croupier Emil), from whom Renault orders a drink when he sits down with the Laszlos. White was a familiar face in many Charlie Chaplin two-reelers in the 1910s, usually playing an upper-class antagonist.
- Frank Puglia as Moroccan Rug Merchant
Much of the emotional impact of the film has been attributed to the large proportion of European exiles and refugees who were extras or played minor roles. A witness to the filming of the "duel of the anthems" sequence said he saw many of the actors crying and "realized that they were all real refugees". Harmetz argues that they "brought to a dozen small roles in Casablanca an understanding and a desperation that could never have come from Central Casting". They were frequently cast as Nazis in war films, even though many were Jewish.
Some of the refugee actors are:
- Louis V. Arco as a refugee in Rick's. Born Lutz Altschul in Austria, he moved to America shortly after the Anschluss because he was Jewish and changed his name.
- Trude Berliner as a baccarat player in Rick's. Born in Berlin, she was a famous cabaret performer and film actress. Jewish, she left Germany in 1933.
- Ilka Grünig as Mrs. Leuchtag. Born in Vienna, she was a silent movie star in Germany who came to America after the Anschluss.
- Lotte Palfi as the refugee trying to sell her diamonds. Born in Germany, she played stage roles at a prestigious theater in Darmstadt, Germany. She emigrated to the US after the Nazis came to power in 1933. She later married another Casablanca actor, Wolfgang Zilzer.
- Richard Ryen as Captain Heinze, Strasser's aide. The Austrian-born Jewish actor had performed in German films, but fled the Nazis.
- Ludwig Stössel as Mr. Leuchtag, the German refugee whose English is "not so good". Born in Austria, the Jewish actor was imprisoned following the Anschluss. When he was released, he left for England and then America. Stössel became famous for doing a long series of commercials for Italian Swiss Colony wine producers. Dressed in an Alpine hat and lederhosen, Stössel was their spokesman with the slogan, "That Little Old Winemaker, Me!"
- Hans Twardowski as the Nazi officer who argues with a French officer over Yvonne. He was born in Stettin, Germany (now Szczecin, Poland).
- Wolfgang Zilzer as the man with expired papers who is shot in the opening scene. He was a silent movie actor in Germany who left when the Nazis took over in 1933. When he applied for his American visa, he discovered that he had been born in Cincinnati, Ohio, while his parents were visiting the United States and thus was an American citizen. He later married Casablanca actress Lotte Palfi. Zilzer had one of the longest careers in the history of cinema; he first appeared in a movie in 1915, when he was 14, and last appeared in a made-for-TV film in 1986.
The comedian Jack Benny may have had an unbilled cameo role, as was claimed by a contemporary newspaper advertisement and reportedly in the Casablanca press book. When asked in his column "Movie Answer Man", critic Roger Ebert first replied, "It looks something like him. That's all I can say." He wrote in a later column, "I think you're right."