According to Sir Kenneth Branagh, roughly thirty Dunkirk survivors, who were in their mid-90s, attended the premiere in London, England. When asked about the movie, they felt that it accurately captured the event, but that the soundtrack was louder than the actual bombardment, a comment that greatly amused writer, producer, and director Sir Christopher Nolan.

In the sequence where the Spitfire ditches into the English Channel, an IMAX camera was strapped into the cockpit to film Collins (Jack Lowden) trying to get out. However, during filming, the plane with the camera still inside sank quicker than predicted. It took so long to retrieve the plane, that the IMAX camera housing filled with water, potentially ruining the expensive camera and the film inside. Cinematographer Hoyta Van Hoytema used an old movie technique of keeping the film wet, and shipped it back to Los Angeles, getting it processed before it dried out. The take from that scene is in the movie.

After first-hand accounts of the Dunkirk evacuation revealed to writer, producer, and director Sir Christopher Nolan how young and inexperienced the soldiers were, he decided to cast young and unknown actors for the beach setting.

Writer, producer, and director Sir Christopher Nolan, along with his wife, producer Dame Emma Thomas, and a friend, made the crossing from England to Dunkirk on a boat, the way the civilians would have done during the original evacuation. Nolan said it took 19 hours because of sea conditions.

The end credits state that twelve of the original little ships that participated in the Dunkirk evacuation appeared in the movie, re-enacting their presence in 1940.

Michael Caine: As the voice of the Royal Air Force flight leader. This is the seventh collaboration between Sir Christopher Nolan and Caine, after Batman Begins (2005), The Prestige (2006), The Dark Knight (2008), Inception (2010), The Dark Knight Rises (2012), and Interstellar (2014). Caine previously portrayed an RAF pilot in Battle of Britain (1969).