The film's initial concept started with a trend Leos Carax had observed where stretch limousines were being increasingly used for weddings. The director was interested in the cars' bulkiness. From that grew an idea for a film about the increasing digitization of society; a science fiction scenario where organisms and visible machines share a common superfluity.
Leos Carax wrote the part of the supermodel with Kate Moss in mind, as they had already been willing to work together in another project that finally was not made. By the time of filming, though, Moss was about to get married and declined the part that, ultimately, went to Eva Mendes.
Edith Scob, who plays chauffeur Céline, starred in the French horror classic Eyes Without a Face (1960), by director Georges Franju. Franju's cinema is the object of several homages throughout 'Holy Motors'. The mask that Céline puts on by the end of the film is a direct reference to 'Les yeux sans visage'.
Leos Carax offered the part of Mr. Oscar's love from the past to his own former girlfriend, Juliette Binoche. According to Carax, they finally "did not get along". He then rewrote the part, made it a singing character and cast Kylie Minogue instead.
The role played by Michel Piccoli was originally intended for Leos Carax himself, but he decided it would be misleading to cast a filmmaker. When Piccoli was cast, the idea was to make him unrecognizable and credit him under a pseudonym, but the information reached the media.