Pitt, who is one of the film's producers, told Entertainment Weekly the actress was "phenomenal in it. That's a tough dress to fill."
"It was 10 years in the making," Pitt admitted of the project. "It wasn't until we found Ana that we could get it across the finish line."
Steve Granitz/WireImage; Netflix
The film, based on the bestseller by Joyce Carol Oates, reimagines the life of Monroe starting from her troubled early childhood to her untimely death in 1962.
The Cuban actress embodied the blonde bombshell of the 1950s and early 60s by showing a side of Monroe rarely seen on screen—Norma Jean Mortenson.
"The film moves along with her feelings and her experiences," de Armas told Netflix Queue. "There are moments when we are inside of her body and mind, and this will give the audience an opportunity to experience what it was like to be Norma and Marilyn at the same time."
Courtesy of Netflix
De Armas also joins a star-studded cast including Julianne Nicholson, Lily Fisher, Evan Williams, Adrien Brody, Xavier Samuel, Toby Huss, David Warshofsky, Caspar Phillipson, Dan Butler, Sara Paxton and Rebecca Wisock.
The film was directed by Andrew Dominik, an "old friend" of Pitt's.
Blonde streams on Netflix on September 28.