She first gained attention for her role as Ames in the second season of the television series Human Target (2010–11), and also for her appearance in the 2009 straight-to-DVD film The Hills Run Red.

Although trained as a dancer at the Stella Mann College of Performing Arts, Bedford, Montgomery chose to pursue acting rather than dance professionally.

While working on Entourage, Montgomery was invited to appear on The League, a critically acclaimed semi-improvised show about American football, and played Ambrosia the stripper in the first episode of the second season.

[citation needed] Montgomery attracted the attention of Stephen Poliakoff via an audition tape she sent to casting director Andy Pryor for the role of Sarah in Dancing on the Edge.

She played Grace Van Helsing, "the prodigal daughter who returns to run the family newspaper (and presumably stake a few vampires)"[4] in the unsold ABC pilot Gothica.

[4] From 2014 to 2017, Montgomery played the lead role of powerful witch Mary Sibley on the WGN America gothic horror series Salem.

[10] In February 2018, Montgomery was cast in a main role in the NBC medical drama New Amsterdam, as Lauren Bloom, the head ER physician.