Humphrey Bogart had already starred in The Maltese Falcon, another Warner Bros film, the year before Casablanca released. Due to The Maltese Falcon being a success for the studio, they were likely confident casting Bogart in Casablanca would appeal to audiences more than an unknown actor would. In 1946, Bogart signed a 15-year contract with Warner Bros.

Ingrid Bergman also had starred in films before Casablanca, such as Dr Jekyll and Mr Hyde, an MGM film, however Casablanca was her first film with WB.

Paul Henreid had starred in films such as Joan of Paris and Now, Voyager (the latter being a Warner Bros film) prior to the film. He also had a contract with Warner Bros, notably because of his accent.

Claude Rains was well known for his ‘character actor’ roles in horror films from Universal Pictures such as The Invisible Man (1933) and The Wolf Man (1941), so being cast in a romantic drama such as Casablanca was a departure from his previous roles, aswell as being with a different studio.

Conrad Veidt was the highest paid actor from Casablanca, and was a famous actor in the 20s for silent films such as The Man Who Laughs (which was the inspiration for the character of the Joker) and The Cabinet of Dr Caligari. Veidt died not long after Casablanca had released.

Sydney Greenstreet, a British actor, was well known for his collaborations with Humphrey Bogart and Peter Lorre, not only Casablanca but also The Maltese Falcon and Passage to Marseille.

Peter Lorre was recognised for the German film M (1931), directed by Fritz Lang, in which he portrayed a serial child killer. Following The Nazi Party coming to power in Germany, Lorre left Germany and went to Hollywood, where he began working with Bogart and Warner Bros.