In the movie Stewart, 23, will be playing the role of Phoebe, the girlfriend of an unmotivated guy named Mike, played by actor Jesse Eisenberg, who live together in a small, sleepy town when their lives take an unexpected turn, reported Daily Mirror.
New Orleans-based hairdresser Maison de Cheveux shared a photo of the actress showing off her new hairstyle on Instagram.
"Kristen Stewart getting her hair ready for a new role!," read the caption of the snap.
Directed by Nima Nourizadeh, the movie will also star actress Uma Thurman.
'American Ultra' is scheduled to begin shooting this month.