Mol's acting career began in summer stock theatre in Vermont where she played a variety of roles including Godspell and 110 in the Shade. She played Jenny in Neil LaBute's The Shape of Things on stage in both London and New York in 2001, in a role she reprised in the film version, released in 2003. The New York Times critic Ben Brantley, in his review of the play (which he disliked), wrote, "[Mol] gives by far the most persuasive performance as the unworldly Jenny, and you wind up feeling for her disproportionately, only because she seems to be entirely there, in the present tense". In 2004, Mol spent a year singing and dancing as Roxie in the Broadway production of Chicago. In 2014–2015, Mol played the role of Emily in the Broadway debut of the Pulitzer Prize–winning Ayad Akhtar play Disgraced.