The director has chosen non-professional actresses to embody the homeless women of his film, with the exception of Sarah Suco and Marie-Christine Orry. He wanted to hire women who had known the street and who had managed to get out or who lived in foster homes. Thus, 150 women were "auditioned" during interviews where they spoke for one hour face camera of their life. Workshops were then set up to observe them in groups and better understand their personalities.
The director met for more than a year with homeless women in various reception centers throughout France, discovering at the same time the profession of social workers, mainly women. He demanded from his actresses the same investment: Audrey Lamy went to a reception center in Grenoble where she helped volunteers to go shopping and cooking. Sarah Suco, meanwhile, lost a lot of weight and made the sleeve several times "to feel the shame and violence of glances" says Louis-Julien Petit.
Despite the difficult subject of the Invisibles, the director wanted to make a solar film and bring hope, in the tradition of Anglo-Saxon social comedies such as The Full Monty, Pride, My Beautiful Laundrette.
The Invisibles was shot in the North of France, which conceals an "inexhaustible" mine of extras "according to the director.
Louis-Julien Petit surprised his actresses by asking them to detach themselves from their lyrics and to privilege improvisation. Audrey Lamy, who had been preparing before the shooting with a coach to know his text perfectly, was disconcerted by this approach.