Apart from the opening shots, Key Largo was filmed entirely at Warner Bros. Studio head Jack Warner -- still reeling from the cost of shooting John Huston's previous film, The Treasure of the Sierra Madre (1948), on location -- refused to approve any more location filming for the director. The pier scenes were filmed using the studio tank with miniature boats in the background to give an illusion of depth. The shipboard shots at the end were also filmed using the studio tank, with fog used to mask the artifice.

Shooting began December 10, 1947.

Although they played on-screen enemies, off-screen Bogart and Robinson treated each other with great respect. Bogart insisted Robinson be treated like a major star and would not come to the set until he was ready. Often, he would go to Robinson's trailer to personally escort him to the set.

When Claire Trevor asked Huston for some insight into her character, he told her, "You're the kind of drunken dame whose elbows are always a little too big, your voice is a little too loud, you're a little too polite. You're very sad, very resigned." (Huston, quoted in James Agee, "Undirectable Director," Life, September 18, 1950). Then he leaned on the set's bar in a way that encapsulated the character for her.

Trevor impressed Huston with her ability to get to the heart of a scene, but she was not sure how to play the scene in which Robinson makes her sing for a drink. She became more concerned when Huston decided to have her sing "Moanin' Low," a difficult song with a wide range. Never a good singer, she kept asking Huston for extra rehearsals and coaching on the song, but he kept putting her off. Then he announced they were filming the scene, put her on the set, gave her a note and told her to sing. Her embarrassment and anger showed through on screen, which fit the character perfectly. When Huston called "Cut," the cast and crew broke into applause.

When Bacall had problems playing her straight leading lady role, Huston twisted her arm to get some emotion into her face.

Huston's scapegoat on the production was Harry Lewis, a young actor cast as one of Robinson's gang members. The inexperienced actor wasn't very good, and Huston browbeat him mercilessly to get a performance out of him. But Lewis would later say Huston was the only director who ever really worked with him. The character's loud clothes and high-pitched laugh were ideas from Huston that helped Lewis register on screen as he never would again.

The Writers Guild nominated Huston and Brooks for Best Written American Drama.

Trevor won the Academy Award® for Best Supporting Actress for her performance in the film. Huston won for writing and directing but for The Treasure of the Sierra Madre, not Key Largo.

By Frank Miller