Marnò landed her first major role in the film "The Stoning of Soraya M," which premiered at the 2008 Toronto International Film Festival. While the film found itself in hot water, the critics praised her harrowing performance
In Seasons 2 and 3 of "House of Cards," Marnò played Ayla Sayyad, an intrepid journalist working for the fictional newspaper known as the Wall Street Telegraph. Arguably, this has been the most prolific role of her career so far, besides that of Samar Navabi in "The Blacklist."
Marnò took on the role of Atti, a sex worker, in the 2014 black-and-white vampire film "A Girl Walks Home Alone at Night." She plays a layered character who is caught between the abusive whims of her pimp and the cruelty of a patriarchal society.