The actor told thelondonpaper that he initially turned down the chance to play the infamous bank robber because of concerns about the tone of the piece.
Cassel said: "It was more than the script, it was the direction of the project that I didn't agree with. I am not a Mesrine fan.
"I'm interested in Mesrine because I'm an actor that's going to play him, and I didn't want to make a hero out of him. He's looked up to as a hero, and he is not."
He added: "Let's face it, the kind of life he had, I would rather be an actor. The truth is you have champagne and you spend money and you have some power, but most of the time you have to hide. That is really far away from actual freedom."
Cassel also stars in the upcoming second part of the Mesrine biopic, which is titled Public Enemy Number One.