Dassin claims his reasoning for the lengthy silence was realism. He explains that this also reinforces their astonishing teamwork under stress and that these men can, and carry these tasks out with no need for words. They work in a state of complete silence where any sound (like Jo bumping the piano) was their mortal enemy. Note that Cesar wears ballet slippers during the heist.

The much imitated heist sequence is over 32 minutes long and contains not a single line of dialogue or music. The production crew and composer Georges Auric thought it would be a disaster to have such a long sequence sans dialogue. Auric insisted that he allow him to write a grand piece of music for the scene and he eventually did on his own. Later Dassin played the part for Auric twice, once with the score, once without. Auric turned to him and admitted, "Without the music".

In the 1972 robbery of the United California Bank, a group of thieves used Styrofoam adhesive to spray inside of an alarm box. This effectively stopped the arm of the alarm from ringing much like the technique used within the film.

The argot slang that the novel was written in was incomprehensible to writer/director Jules Dassin, so much so that he had to have the producer who suggested it, read it to him. The producer initially refused because he had been courting a woman for some time and had "plans" that night. Dassin told him that he'd lost his woman and that he had to come over and read it to him (which he did). When he finally understood the story he claims that he was "shocked" by its content (the story involves necrophilia, amongst other things) and was prepared to tell Henri Bérard that he didn't want to do the film. What changed his mind was his blacklist-induced poverty. He then cut Auguste Le Breton's novel down to a story of a heist (which was only a small element of the actual story). Le Breton was infuriated and came to Dassin and asked, "Where is my book?". Dassin explained the situation to him, but Le Breton ignored him and simply repeated "Where is my book?" until eventually drawing a pistol and placing it on the table as a threat. Dassin claims that the threat of violence over such a matter and the appearance of Le Breton was so ridiculous that he simply broke out with laughter. Le Breton then laughed and the two got along fine, despite the disagreement.

L'Age D'or, the club in the film, was named after Luis Buñuel's film of the same name. Production designer Alexandre Trauner worked on both films.